I don't recall any Brits in the original Transformers except for Wreck-Gar, and he wasn't G1 anyway. The voices weren't the same, but they were good enough considering how little they said. Other than Prime and Megatron most lines went to new characters. Considering how little screentime any of them had that wasn't fighting, as opposed to the cartoons that spent all their time with them (because in animation it's the same cost to do robots or people while in a live action film the robots cost big $$ every shot you see) it doesn't surprise me you don't see much characterization.
As for Starscream aka Cobra Commander, the actor, Chris Latta, died over 15 years ago. I just don't know who else could've done that voice. The guy who does it now, including in the films, was actually in the original GI Joe as well, playing Low Light, and in the original Transformers, playing Silverbolt, so at least he has some pedigree.