Right so I'm very very very pleased to say that I found an absolutely beautiful Gibson J50 from 1972 fitted with a pickup that plays absolutely beautifully. I just picked it up and it felt like my guitar. I couldn't actually put it down, it just felt right. Got it from Angel Music in Denmark Street which is an excellent shop and completely hidden. It's upstairs above another shop, you have to press a buzzer to get in... and when you do... wow! Andy there has got lots of very affordable vintage guitars and much better prices than anywhere else in London. It needed a minor repair which he offered to get done for free and then it's ready! I cannot wait.
By the way, I tried out a lot of new Gibsons including the EJ200 and a couple of J45s and to be honest I wasn't as blown away as I'd expected to be. Something about the newness of the wood or the veneer perhaps, but they sounded a little plastic-y to me (obviously I'm talking shit really, they were great, but not THAT great). One of the J45s was good but it cost £1600. I would definitely take the old guitar over it any day of the week and it was almost half the price.
I can't wait to start playing the guitar. In the meantime here's this rather bad picture...