boz,
There are a couple of good sites in the UK where you may find someone more familiar with your engines.
There's a lot of "rare and unusual engine" info on the Barton Model lfying Club site, for example:
http://www.controlline.org.uk/phpBB2/index.php
Just Engines has a manufacturers' site that may help.
http://www.justengines.unseen.org/
Ian Russell has been around our engines for a long time, and may have some thoughts on this, too. I don't have a URL for him at hand.
Luck! It would be a shame to harm your engines with a wrong fuel...