If your budget can stretch to it, have a look at backpacking tents - they tend to be lighter and smaller (and more expensive). Check out the 'Go Outdoors' site and if you have one close to you, pop down and have a look, they have tents on display.
I would second the idea of a 3 person tent (for extra space), something like the Vango Tempest 300 (£100) or the Vango Omega 350 (£130), or if you want to stick with 2-person, perhaps the Vango Tempest 200 (£90). The Go Outdoors website also gives 'pack size' for some of the tets, eg the Tempest 300 is (cm) 58 x 16 x 14