I have got some thinners and soaked one set of the jets for an hour and it has made zero impact on the varnish. Will leave it overnight and check it again in the morning but at the moment it looks like new jets are needed.I have found the pilot jets online for a reasonable price (not Fowlers £8 each) but cannot find the main jet 0.6 anywhere other than fowlers at the moment. I will call my local place and check with them in the morning as he has a selection box of different main jets in stock if the thinners don't work.
It has to be cellulose thinners the stuff used by spray painters not ordinary paint thinners