Build a timber framed cartlodge/grarage.
We built a very basic storage shed last year for a regular customer last christmas. I'll pop out and take a picture of it for you to see the size and style. The labour and materials came to around £7K i think. Its bricked on footings up to over site, then simple 4"x2" frame and hand cut roof.
Its fully wired up, boarded and plastered, and the windows wernt cheap either, so probalby a cartlodge this size id say about £6k.
Heres a pic of my cart lodge, just to give u an idea untill i get a pic of the one im one about.
On the other hand, we have also constructed i think 6 "flat pack" buildings from sweden. basically they are just giant 3d jigsaw puzzles. quality is very good.
you just need to screed a level floor base and away you go. but from memory id say an equivelant one to the size above and that u require for 4 cars, id say just the flat pack would come in at over 10k! then you have concrete and labour on top.
The beauty of these tho is you can avoid planning as they are seen as a non permamant structure.
So basically unless your perpared to spend at least 5k+, i dont think your going to get anything that you want.
A lot of people i have seen just buy the small marquees (sp?) which each one could hold 2 cars. I know someone in the village whos restoring a 2WD saff and a Vw camper van in one!!
You can pick these up for about £300 each for the 2 car size.
May be your best bet, if moneys tight, and also dont forget you can take these with you if you move!!
heres a massive one, tho it would be cos its american!