Maybe they're not the ones after all? Then Thomas' name seems pretty unique. (Maybe the transcription is wrong and the old writing of 'ss' was mistaken for a p? I see the GRO has her name as Burgess)
Here they are with Thomas' parents in 1851 - any use?
1851
HO107/1919 166 30
St Just, Cornwall
Carnyorth
Richard Pryar, head, 41, Miner, b. St Just Cornwall
Mary Ann, wife, 43, b. Penryn
Thomas, son, mar, 20, Miner, b. Marazion
Mary, d law, mar, 22, b. Breage
Allace, dau, 11, b. Marazion
Mary Ann, dau, 10, b. do.
Elizabeth, dau, (age column shows a 3 in the male column and a 6 in the female), b. do.
Richard, son, (no age shown - I'm guessing he should be 3), b. do.