You can order a copy of his birth cert from at the cost of £9.25. They take credit cards.
http://www.gro.gov.uk/gro/content/certificates/You need the GRO ref
Percy Powning Trestrail march qtr 1886 Redruth vol 5c pg 233
Perhaps he added a year to his age to join up earlier?
census as promissed
1851 North of Trevassack, Phillack HO107/1916 folio 662 pg 47
William Trestrail head mar 32 shoemaker
Eliza wife 29 b. Perrranuthnoe
Mary jane dau 6
Elizabeth Ann dau 2
all born Phillack except where stated
1861 Back Row, Hayle RG9/1586 folio 100 pg 37
William Trestrail head mar 43 shoemaker
Eliza wife 40 b. Perranuthnoe
Mary J dau 17
Eliz
th Ann dau 12 blind
Charlott dau 6
Thomas son 4 months
all born Phillack unless otherwise stated
1871 Prospect Place, Hayle RG10/2327 folio 72 pg 61
William Trestrail head mra 52 shoemaker
Eliza wife 49 b. Perranuthnoe
Thomas G P son 10
Eliza Emily dau 4
all born Phillack unless otherwise stated
1881 Prospect Place, hayle RG11/2337 folio 66 pg 57
Wm Trestrail head mar 60 shoemaker b. Phillack
Eliza wife 58 b. Ludgvan
Minnie dau 14 b. Phillack
you can get transcriptions of the Cornwall census here
http://www.freecen.org.uk/cgi/search.plAs there seems to be no sign of baptisms in the Phillack records, I wonder if the family became non-conformist?