A caution on Penetrol (not a cleaner, btw) - it's extremely effective at "restoring" chalky gelcoats, esp the deeper colours.. but it's temporary and makes subsequent painting difficult. All traces of it must be removed prior to painting,- it does "penetrate" the surface so it's difficult to know for certain it's all gone - and could lead to unsatisfactory results with the new coatings.
Heinzir: Pretty shippy little boat!! Nice.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"