Blue Peter Sailing Dinghy - Clean Prior to Repair

The difference Y10 made. Spotless!

Issues with Gelcoat

Having cleaned the hull with Y10, its looking really nice and blue now. All hint of the yellow to red tinge has disappeared. I can envisage getting this side to look like new.

Sadly, I can't seem to shift this discolouration on the inside (topside) which is really concerning.

I've tried Y10, Star Brite Hull Cleaner with PTFE, and PVC window cleaner (a bit like Cif).

Any other ideas, or am I stuck with it?

Inside of starboard seat and transom corner
Inside of starboard seat and transom corner
Inside of starboard seat and transom corner
Inside of starboard floor and transom corner
Inside the hull through an access panel - black mould spots?
Inside the hull through an access panel - black mould spots?
Exterior of Transom - wood is mounting for rudder
Builders plate 1
Builders plate 2
Writing on exterior - comic sans?
Writing on exterior - comic sans?
Inside of cockpit showing ?spine? of boat closest to bow
Bow end of Port Seat
Dagger board slot - lots of crazing and two halves of hull not joined
starboard of bow end of cockpit - stress indent - pops back in if pressed out from inside hull (fibreglass side)
Very multicoloured
Very multicoloured