Ok then, well I had a play of it yesterday.  It played nice, and the neck felt good/ the tone and feel was very suggestive that it was a mexican fender Jazz.  I haven't bought it yet, may well do so tonight. 
 
I noticed one thing, the neck plate was plain, no logo.  Do mexican fenders have a logo on the neck plate? 
 
Now the bad ass bridge.  Is it usual for a bad ass bridge to be modified as such with holes through the body?  I thought they were a direct replacement for the bridge already on it?  If it was a standard jazz surely it would have been more work to drill holes.... 
 
The seller did say it had been installed in a shop on denmark street, not that he had any verification for it. 
 
edit: i didn't check the ferrules on the back, will do when i look at it this evening.