Here's an idea:

1) Destroy your census form.
2) Wait for them to contact you about not having sent it off and claim it must have been lost in the mail.
3) Wait for them to send you another form.
4) Fill the form out with the most obscure answers you can think of - including Jedi - and post it.

Now all this will not really cause much hassle to the government, but if you hate them as much as I do you'll take the view that every little helps and each act of resistance is worthwhile and can be an individualist end in itself. Above all it'll make you feel good, kind of like when you send heavy things to freepost addresses. Abuse the force.

What I *don't* reccommend is adopting the moral high ground and refusing to comply with the census. They'll force you to pay the £1000 fine eventually, and that money will just be spent on more censuses, DNA databases, CCTV, GCHQ wiretaps and other intrusions of our privacy.