i don't think american-style jelly really exists in britain. british jam and american jam are mostly the same thing, if encountered it would probably be called filtered jam or clear jam.
Conserve is the antiquated term the British would probably use if 'filtered jam' existed there.
Jam has small bits of fruit (usually like strawberry/raspberry seeds). US jelly does not since it's made from juice or syrup. Preserves are the kind with bigger chunks of fruit.