Thanks very much folks
The glassed in 'non' thru hulls seem like a great idea so I'll certainly leave those well alone.
I was only thinking of changing the ball valves at some point as they seem to be newly fitted but made from no marine grade metals for household purposes.
I'd be really interested to hear what valves the early Amels originally came with? It'd be nice to try and move back to something more original.
In terms of how to remove these ball valves it Sounds like I just hold the glassed in section nut tight and unwind the valve and voila - swap the ball valve out
Many thanks for help and support
All the best