Newton Ellis & Company
29 Cheapside
Liverpool
L2 2DY
England
Tel. 0151 236 1391
They are very good, particularly with older equipment, and I am sure could AI your Nikkors if anyone can, although as I recall this officially requires a conversion kit which is no longer available.
I had a lens AI'd a few years ago by Fixation in London. They made a good job of milling the rear end (as David said the conversion kits are no longer available). I seem to remember the cost was something like £40-50.
Their new address is:
Unit C, 250 Kennington Lane, SE11 5RD. Tel:020 7582 3294 Fax:020 7582 9050