US and UK stories are essentially one continuity, with some discrepancies here and there. Basically the UK comics were written as an "expansion" of the US comics, but occasionally there would be discrepancies because Budiansky and Furman weren't cooperating -- pretty much Budiansky wrote the US comics, and it was up to Furman to expand on it in the UK comics. Sometimes the UK stories would digress from US continuity at behest of Hasbro UK, like the Earthforce Saga, which was written to promote the Classic G1 reissues. But that story has since been retconned as out-of-continuity* anyway.

And when Furman took over from Budiansky in writing the US comics, he cemented the US continuity even further into events that occured in the UK comics. The Matrix Quest is a classic example of this -- even though Matrix Quest was a US story, the precursor events that led to it occured in the UK comics and the US comics even had flashbacks to events from the UK series! (e.g. Optimus Prime's original body being buried in space aboard a funeral barge, Deathbringer etc.)

There's always room for writers to try and resolve some of the continuity discrepancies between the US and UK G1 stories, but that doesn't make them separate continuities per se... the UK comics were intended to be part of the same continuity as the US (and vice versa when Furman took over the job of writing the US comics).

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*Having said that, in US#75 when Grimlock uses the Ark to smack Unicron across the face, there's this reference/tribute to Earthforce.