Chris - you mention the excellent transcription of the 1851 census
Have also checked all 23 volumes (over 200,000 names) of June Barnes
Census Transcription of the 1851 census for East Sussex - and he aint there.
However, it is worth noting that the booklets don't cover Brighton, Hove or the Preston area in the north part of modern Brighton.
There are transcriptions done more recently now for part of Brighton in 1851 (the "Level" area), but I don't think there have been transcripts published for the rest of the town yet. I'd love to hear if you know of any progress!
There would be alot of work involved in covering the whole of the town. The population of Brighton almost doubled between 1841 and 1871 (from 46,000 to 90,000).
I'm seeking a HILLMAN family from Brighton myself: Elizabeth Gasston HILLMAN born about 1829 (but in Southwark, London by 1851). She was the daughter of an Edward HILLMAN (who was deceased by her wedding in 1855). Witnesses at wedding were an Elizabeth and an Edward Henry HILLMAN.