Well, some of those clues that might help!
I tend to think of Hampshire as south of England. West of England is Somerset, Devon or Cornwall for sure and maybe Wiltshire and some other counties.
Penryn in the parish of St Gluvias is not contiguous with St Martin Looe - in fact it's quite a hoof along the coast. So this is quite a confusing picture

The William baptised in 1820 in Stithians - his father was a miner at Wendron, rather than a soldier

unless he joined up afterwards? Lots of miners in Cornwall of course.
Did you consider this baptism?
William Collins bp 27-Aug 1820 Perranarworthal, son of William & Mary Collins, miner of Gluvias
Nell