I've been looking into tents recently. Funnily enough. Most of the tents I've seen that look half-way decent are ?80+, except the "festival tents" - i.e. dome tents that have no porch space (for boots etc) and will most likely be thrown away after a weekends use so build quality is not likely to be great.
I was in Black's yesterday & was going to buy their ?75 2-man tent. It's lightweight & rugged, but then I spied the following in Millets for ?40. It's not likely to be as water proof as the Black's one, but at half price I can live with that & buy some sealent! It's compact & lightweight, ideal for slinging on the back of the bike. And for £40 I won't wince so much if it falls off the back of the bike and I don't notice!
For those going to the AR08 it might be ideal!
http://www.walkmag.co.uk/gear/tents/..._two_man_tent/
Edit: Just put some silicon-based sealent on the outer-skin, which cost me the princely sum of ?6.50.