Many thanks for all that info and the links, xiphophilos. I thought somewhere in 45worlds or 45cat forums there might be something relevant to find. As ever, it's easier when you know what you're searching for... Yes, Holton heath is west of Poole and thus 40 miles West of Southampton, though a rail link from the site would have made transport to Southampton & the docks there considerably more straightforward than by road. I'll see if I can research any further. As I've said - probably not at all relevant to this release but a very interesting tangent nonetheless.
This must be the Decca plant in Holton Heath that was active in the 1950s and 1960s; PhilMH mentioned in a 45cat Forum post that he suspects they pressed London 78s and 45s as well, although an article in Hillandale News 131, page 181 claims it was opened "primarily for the production of 45rpm singles."
Apparently, the site was first used by the Royal Navy Cordite Factory; Decca installed an FFRR sign on the old boiler house of that factory (source); all this was later demolished. I also found the claim that the site is now used by Heatric (source), whose current address is 46 Holton Rd, Wareham Lady St Mary, Holton Heath, Poole BH16 6LT. Maybe you can still find the dump of failed pressings nearby (source).
Don't know if this helps - or is even relevant, but here goes...probably belongs with UK artist release.
Looking at the comments about London UK pressings, It's possible some may have originated from the then-new second Decca plant in the UK - not New Malden . I've seen a couple of references to a factory opened in Southampton about 1948 specifically for export. Southampton was a key port for transatlantic crossings.
If there's any identifier on these pressings, assuming both 78s and the LPs were pressed there, I can't find any reference to it. Indeed I've failed to find very much that refers to this plant, and I can't find out where it was located(I live about 15mls away)
There is no way to distinguish a London pressing with 'Made in England' as being destined for Canada or the USA. Some pressings actually exist with 'Made in England', 'Made in USA' and 'Made in Canada' variations. Surely some 'Made in England', such as George Formby, are more likely to have been for Canada rather than the USA. One possibility is that London did initial pressings in the UK, then if a record took off, did local pressings to more rapidly meet demand.
Should they be listed here as UK Export? No, because in most cases no USA or Canada equivalent exists. Ideally what should be a hybrid 'flag', of USA/Canada, such as we have for international
Is there any way to distinguish Canadian black-label International releases on London from their U.S. variants? I can't see any, except that many Canadian releases seem to say "Made in Canada". Or is this, in fact, a U.S. release?
Apparently, the black label series was established in Sept. 1948, at the same time as London's Canadian branch, and both were supposed to "handle the new black-label International series," cf. Billboard, Sept. 11, 1948, page 19.