Thanks Miker and everyone else.
I tried a mixture of all suggestions except for the pool and the iron. I decided the risks of doing more damage was not justified.
Did also guerney them prior to hanging up to dry.
Sails are now folded up ready for their return journey.
Much cleaner, still not snowy white, but have they ever been?
I still have my fingers attached to hands so the chemicals can't have been that bad.
The thing that did some damage was a good scrub with Jif and the scourer. Even though brief I decided that abrasion was probably not wise.
Miker, re your iron idea... It brought back nightmares of when I was a bridesmaid and the mother of the bride decided to iron the veil 2 hours before the wedding!!!
I did not want to get the same iron shaped hole in my sail.
p.s. The bride still got married in a veil borrowed from a cousin. I sewed the tiara on it whilst trying to keep the bride calm. They are still married, so the veil must have become the something borrowed.