I have been using Epiphanes varnish for a couple of years. It works very well for me and doesn't smell as bad as nitro or many other finishes & it cures very quickly. It's made in Holland, so I think you should be able to get it in the UK. I have been buying it from Jamestown Distributors in the US:
http://www.jamestowndistributors.com...iphane_varnish
All the octave mandolins on my website are finished with it. It has a very nice glow to it, and can be buffed to a high gloss.
http://jmendelfrets.com/Sub_ForSale.aspx
Good luck finding a new finish that works well for you.
Joe