I'll put in a couple of recommendations for fellow English members, if close by...
Technasales in Northcamp, Farnborough, Hampshire, 5 minutes from the M3 motorway, looks like a normal high-torquestreet shop, up front is a new tool sales area, taps, dies, drill bits etc, mainly consumables, out back is the secondhand stock, much the same kind of stuff, but a good part is usually the difficult sizes / standards like Whitworth, BSF etc.
10 minutes away is AHC in Camberley, Surrey, good selection of consumables plus a very good range of fasteners, and guys who take the time to look if you're after something unusual!
Not associated, happy customer etc.
Dave H. (the other one)