It depends on what you're looking for.
If you want a robust, well built guitar with a good sound for gigging and recording, I'd suggest somewhere in the region of £500 should do you very well. BUT it depends on so many things. For example, if you're not a great player, the best guitar in the world won't make you sound any better (although it will possibly make you look better)
For example, I like to think of myself as a medium-good guitarist, and I have an American fender tele with a vox valve amp, and I think the quality is matched perfectly to my ability and needs. Acoustic-wise, I'm a bit under-represented. My guitar is fine, but it's not great recorded, and I think I'd do well to upgrade to a cheap Martin or similar.
But if you're looking for something that's going to hold its value, form part of a collection, or just be a one-of-a-kind job, then it's only limited by your budget. There are some very expensive guitars out there. You only have to justify the expense (and have bags of cash!)