Rob,
I don't suppose you get Popular Woodworking from the US, do you? Pretty good run down about wipe on poly in the November issue. The gist seemed to be you can quite easily make your own, and it's worth doing 'cos it's the bee's knees. Thin any varnish which has white spirit given as the clean-up solvent 50/50 with white spirit and thin further if desired, seems to be the essence of the thing. I've never tried it myself, but I was tempted to give it a go, I must say.
Cheers, Alf