In reply to JonLongshanks: The best deal I am currently aware of is that the North Face Outlet at Bicester Village had several Westwind 3 going for the crazy price of £145 on Sunday. FWIW they also had a Westwind 2 and a pair of Tadpole 2DL for similar money.
Otherwise at your budget you are pretty much limited to trying to get a decent deal on a Vango. Plenty of other cheap makes are available but especially if you shop around you can't really beat Vango when it comes to value for money. The Vango Tempest 300 is a good tent and the only 3-man option around the £100 mark that I'd really like to carry personally for general backpacking.