Welcome matey,
All the resources you need to find your ideal Zed will be on here.
I managed to pick up my UK GT pack last year for about £9.5k. For your money you're probably either looking at a Jap import or a higher mileague UK like mine.
I'd say you're better of going with the later as it's easier to follow the cars history, where i'ts been and what it's been through. Also, a lot of insurer's don't like imports so you may end up paying more in the long run going down that route.
Whatever you decide the engine's are rock solid and go on forever (like all Jap cars) and as long as they have been serviced regualrly (every 9k) high mileague isn't somehting you should fear and certainly doesn't mean what it once did.
Just take your time, read through the many, many, many threads there are on the forum about buying a used Zed and I'm sure you'l find your perfect Zed for a price thats right.
When you find a specific car that you may be looking at buying, put a link to the ad and pictures on the site. There's a massive pool of Zed expertise here and we may be able to spot something a miss that you may not have noticed.
Good luck!