Many thanks to Ray for publishing those informative price lists. I have a Vox price list from 1965 and a Burns list from 1967, but not much in the way of pictorial illustration (though there is some).
There certainly seems to be a lot of confusion regarding the availability of roundwound strings at the dawn of the beat era, and about whether Hank ever used flatwound strings (see below). Another confused item - not just here, but all over the internet (again, see below) - is the nature of Gibson Sonomatic strings. I've said it before, but feel that it's worth saying it again: there was no such thing as a flatwound Sonomatic string.
Sonomatic = roundwound (always).
The early sixties Gibson range of electric guitar strings consisted of three "models": Sonomatic (roundwound and 13-56 [definitely
not starting with a 12*]), Hi-Fi Flatwound (same gauges) and Polished Compound Bronze (same gauges and a cross between round and flat in terms of feel). The PCB strings were intended for acoustic or electric guitar, but they were expensive in the UK and I only ever met one guitarist who used them (on a Harmony H77).
[*The current L5 Gibson strings are impostors - only one gauge of the set is the same as the original Sonomatic E340s]
Did Hank use flats on the Strat or other quality electrics? If he says not, I'm inclined to agree. There is no real sonic evidence of them once the hits start flowing, and plenty the other way round. But on the Antoria guitar there is clear evidence of the use of flatwound strings in the first half of 1959. Roberto Pistolesi obtained large high-res copies of well-known pics of The Drifters, with unmistakeable images of the sheen of tapewound strings on the Antoria and even a knot in a string (above the nut) on Jet's Besson bass - clearly indicating that money was still an object.
Were roundwound strings available in the fifties/early sixties in the UK?
Definitely. Every brand of the time offered roundwound - some offered only roundwound in the UK (eg, Black Diamond). Roundwound strings were offered by Hofner (likely made by Pyramid), Cathedral and Monopole (the ancestors of Picato), James Howe (at first via the Vox and Burns brands, then Rotop, finally Rotosound).
Flatwound strings were always a more expensive option - but an option, and certainly not "the only thing you could get".
Try a few URLs for an interesting range of historical slants (but beware of tripe such as "flatwound Sonomatics"):
http://www.guitarplayer.com/article/pure-nickel-strings/8326http://www.rickresource.com/forum/viewtopic.php?f=7&t=12696http://www.thewho.net/whotabs/gear/guitar/strings.htmlhttp://forum.gibson.com/index.php?/topic/15469-early-strings/http://magazine.dv247.com/2011/02/16/electric-guitar-strings/And what about these (from the mid-sixties, complete with gauges)?