^ +1
up the budget to £300 and you can get a 612V. it has grover locking tuners, so that wouldn't hurt with the staying in tune thing. also, since you have BKPs ready to put into it, you could sell its Duncan JB to get a little money back, which would hopefully bring the overall price back down closer to your original budget of £250. i've actually only tried the 112v and 812v, but assuming the 612v's quality is closer to the 812v, that'd be my choice.
those vintage advances can be quite variable (as i just said in another thread)- some i've tried have been nice, some not so nice. i wouldn't really want to buy one off the net, to be honest...