Bob Jackson have a mixed reputation for framebuilding, with tales of people receiving custom frames with bizarre geometry, and my own experience is that their framebuilding QC is poor, although their painting is good. An off-the-peg frame will fit 99.9% of people anyway, and the other 0.1% are probably just being vain.
Among really good secondhand frames, Ron Cooper's frames are good if you can find one (he built over 7,000 so it shouldn't be that hard, although how many non-full-on race frames he did, I don't know). Also look for George Longstaff and Tony Oliver, who mostly built touring style frames, Dave Yates and Chas Roberts, who built anything. Going cheaper, you're into medium volume builders like Mercian. Go much cheaper, and some Orbits can be good, as can Nigel Deans. The older you go, the more likely you'll need to stretch a rear end from 126mm to 130mm and find a 1" headset size - so you'll either need to live with a quill stem, get a replacement threadless fork, or have a threadless steerer brazed onto an original fork (wouldn't recommend the latter two as 1" Aheadsets are a bit rare, whereas 1" quill stems never went away).
You can go for real vintage 50s stuff with curly lugs but you will definitely have a 1" headset, possibly no braze-ons at all (not even cable stops on a road/path frame, certainly not bottle bosses) and the rear end could be anything from 112mm to 120mm. To have the necessary braze-ons added, a repaint that does the frame justice, a re-space and a re-track, expect to throw £400 at Argos in Bristol, a bit less for other shops.
Watch out for steep seat angles of 73 or 74 degrees on Taiwanese-built frames like Paul Hewitt's. These are a bit of a pain if you want to use a Brooks saddle (short rails) and you'll need to hunt around for a seatpost with serious layback. A 71 degree seat angle is better for a Brooks but I suppose it doesn't look racy enough these days. On the subject of Hewitt, the touring frames are very nicely specified and finished but are more suitable for unloaded audaxing than for loaded touring. My Cheviot is impossible to ride out of the saddle with a camping load on the back, a problem its predecessor (a Thorn Nomad) never suffered from. The lighter version of the Cheviot might be worth looking at.
