I support the aims of the demo but you may be interested in the following approach. Apologies if you have already tried it or decided that it won't work in the cases you work with! I approached a Midlands-based Citizens Advice Bureau a few years back in the case of my hot water failing in my rented flat. The landlord - a difficult and argumentative man - took some five weeks to initiate repairs and so I was keen to see what legal recourse I had.

It turns out that providing a tenant has written to their landlord complaining about poor conditions, and the landlord has demonstrably done nothing in response, rent can be spent legally on reasonable costs to fix issues. For example in the case of pest control, written quotations from a few local firms could be obtained, and the 'best value' quotation selected by the tenant. Copies of the paid bill should then be sent to the landlord, and the amount may be subtracted from the rent.

A tenant who takes this course of action should not suffer any threat of eviction or accumulating punitive charges for monies withheld, as it is perfectly legal. Naturally anyone wanting to undertake this action should get CAB or legal advice - I am not a lawyer! (Incidentally by the time I received this advice, several weeks into my hot water woes, the boiler installers were booked and ready to come. Therefore the advice came to late to help me, but perhaps it will help someone else.)