I suspect that the differing attitudes to sleeving of cylinders ( which was much discussed in a thread a while ago ) is related to the fact that UK tuners and builders have a long-standing practice of increasing engine capacity by increasing the bore, whereas stroking is not usual. This is in turn, because many British designs of the 40s, 50s and 60s are designed to be used in this way ( typically 350cc and 500cc, or 500cc and 650cc versions of the same engine ) or have well-established 650cc - 750cc conversions ( Morgo et al ).
Regarding cams, welding cams that way has probably never become accepted here because there are other ways of achieving the same thing. Norton and Velocette had a vernier adjustment system on the single-cylinder engines most likely to be subject of such attentions. At least one current tuner has developed a similar syatem for the BSA Gold Star. Many British twin-cylinder engines had cam drive gears which were pressed onto tapers and retained by nuts, so no welding is involved; the problem being to fit the drive gear accurately in the first place, a job which is done with the camshaft already in the engine. The four-cam style design used on the WR, KR and XR is not usual on British singles, and since virtually all designs since the 30s use solid, rather than roller, followers minor adjustments can be made by stoning the follower shoes, again a simple dismantling and reassembly procedure.
As has been remarked above, getting the attention of engine builders is an arbitrary process, and from long experience the chances of getting them to do something they are not accustomed to is zero or somewhat less.
Mongo only pawn in game of life