You can create ventilation ducts within the plastic canvas by designating a top part to the canvas, closer to the middle if you plan on attaching it to string and hanging it up between trees, and ensuring that the rainwater cannot run into any area of the interior at any time as it moves down the exterior of the canvas towards the ground. The ventilation can then occur by puncturing holes in the canvas and placing on top of that hole another piece of plastic that is open at the bottom end and closed to rainwater at the top end.

Another great thing about this is that broken areas can be fixed simply by applying another piece of plastic above it and ensuring that rainwater runs around it. More air as well!

If you draw out a plan for the canvas ensure that you remember the rope will probably be running somewhere closer to the middle if you mean to turn it into a personal tent, and also that at no point can the rainwater enter the interior of the canvas during its journey to the ground.

Ventilation can be created by leaving open areas of the canvas in which no water can run into.

Should a hole appear in the canvas then simply find another piece of plastic and attach it so that the sections are sealed at the top of the canvas to ensure that there is no leaking.

And perfect for use with a hammock.

When I was lying there on the tarmac, my biggest fear was having to end the protest because my bladder couldn't take anymore. You are committed for hours but you don't want your piss to dribble on your fellow protestors if you 'need to go'. I got around that by getting a bit drunk the night before and so urinating a lot before the protest. It dehydrates you. Plastic pants for incontinence would be a good alternative, maybe other folk here have better tips but I think they are shy of sharing them.

Also, I've got really bad circulation, I get cold quickly. And lying about on tarmac gets anyone cold quickly. So this is a bit yuppie maybe, certainly unenvironmentallly friendly, but you can buy little pouches that keep your hands warm when you shake them.

Oh, and if you are a smoker and expect to be arrested, nicotine gum secreteted around your person helps pass the time in the cell.

Your idea of supergluing carrier bags together is loopy, it would leak like a sieve and fall apart. If the intention is to recycle materials then you need to also consider the super glue and duct tape. Super glue costs a fortune - 5 ml for several quid which is more than vintage champagne. Part of the reason for this is that an elaborate cocktail of chemicals are needed to manufacture it so that wouldn't be very eco friendly. Also carrier bags are so flimsy that the whole thing would rip apart in the slightest breeze. Much better would be to use a sheet of heavy guage polythene as sold at builders merchants. This would last for up to 2 years but the UV from the sun will make it go brittle after that. Polythene being the simplest molecule of any of the plastics has quite a low environmental footprint compared to all that super glue and tape.

For staying warm, people need to pay much more attention to the choice of materials they wear. Too many activists are fashion junkies and insist on wearing rainbow holey jumpers as their outer layer because it looks cool. Well it certainly is cool as the wind cuts right through such a permeable garment. Much better is to wear a waterproof windproof jacket on the outside even when it's not raining. Also don't wear cotton - trackies, sweatshirts, socks etc. Cotton is a summer fabric. Have you ever noticed how cold your legs are when you're soaked to the skin wearing jeans? Once wet cotton is incredibly cold, weighs a ton and takes days to dry out. Check the labels and wear layers of fabrics like acrylic and polyester fleeces which absorb very little water, are still warm when wet and dry out extremely quickly. You can buy cheap and cheerful fleeces at street markets for not very much cost. I find that some of the lined ones have open pore foam under the lining which is crap when wet so you may consider cutting out any such lining to improve them. Wool is reasonably warm when wet but still takes ages to dry so isn't very practical if you're living out in the woods without drying facilities.

When sleeping out, as well as having a good sleeping bag, you need to have a really good insulating layer beneath you such as a closed cell foam mat to prevent heat loss into the ground. This is much more important than piling extra layers on top. The best sleeping bag in the world won't keep you warm otherwise.

If your extremities become cold, this usually means your core body temperature is reduced so paradoxically, wearing more body layers can be much more effective than buying expensive gloves or socks. Gloves are expensive but I've noticed that during any cold spells, there are loads dropped in the road by bus stops presumably by people fumbling for oyster cards! Also remember that your brain receives 25% of your blood supply so wearing a wooly hat is really important especially if you have short hair.

If you're lying in a road blockading or similar then the hard cold road surface is likely to rapidly suck heat from your body at all points of contact. Since the cops are likely to deliberately remove any insulated mat that you lie on to make you more uncomfortable, you may consider wearing strips of insulating foam inside your clothes covering the areas of contact - buttocks, backs of lower legs, shoulders, elbows etc. As for the problem of not being able to wee - well the obvious thing is not to drink gallons of tea beforehand. Short term dehydration may give you a slight headache but it never killed anyone.

Oh, I forgot. Goretex is cool AND warm. Keeps the rain out and lets the sweat out. I know that is a tradename but I'm not recommending buying it, too damn expensive. Find your (my?) local factory and take a day-trip. They have rubbish skips full of the stuff. Rather impolitely they have padlocked them so take a set of bolt-cutters. And if you are being polite then leave a new lock. They have CCTV - it is a cynical world. Unless you get lucky you will need access to a sewing machine to make anything useful from the offcuts. You will look like a multicoloured patchwork scarecrow but I know how that is most of you would choose to look anyway.

You can buy a heavy 20-15 foot tarpaulin for about a tenner. If you are out of the rain and can start a wee fire then you can survive even the worst of Scottish weather comfortably most of the year nowadays in just a bivvy bag. Which is worrying.

You don't always notice hypothermia setting in, it creeps up on you. Changing colour is a sign - going grey is very bad ! Hearing voices is bad too - as is not hearing external noises. At that point, your fingers will already have stopped working. If you get to that stage, and you have't seen too many Ray Mears videos, then you have two choices, seek urgent help or something elses body heat, or go to a deep, deep, comforting sleep.