Which Fuel Proofer?

Have you painted the wood at all yet? If not, I don't know if Rustoleum spray enamel is available in England, but it's very fuel resistant as long as you let it cure for a week. I use the Automotive if I can get it, but I don't know if that's better or not. The lighter colors are said to be somewhat more fuel resistant than the darker colors, but they've worked just fine for me too. The metallic colors are NOT fuel resistant. Castor goo doesn't bother it much at all. The same goes for Krylon brand spray enamel paints. Maybe someone in the UK can recommend equivalent brands.

If I have a new model, I usually seal the firewall and vicinity with 30 or 60 minute epoxy, thinned with acetone so it can be brushed on. It may leave a bit of a wavy finish if you lay it on thick, but it's impenetrable to fresh nitromethane and alcohol. It's too heavy to do the rest of the plane with though.

The spray paint looks best on balsa and soaks up less paint if you spray on some light gray Rustoleum automotive primer and lightly sand it before putting the colors on. For added protection I usually use Top Flite Lustrekote clear gloss. Wait until the paint is fully cured before applying the clear. It's heavy too, so sometimes I only spray the front end. On areas that you don't use it, you'll see some faint color come off on your alcohol rag during your post flight cleanup. But it still looks good and so far I've never rubbed all the way through it. I hear the Rustoleum clear is just as good too, but never tried it. Only do light coats of clear until the last glassy coat, or it may craze the paint, making it bubble up. Seal the water slide decals with it too, but be even lighter handed and let it dry fully before the final coat.

Just keep in mind, go slow and be patient so it takes less paint weight to get that pretty finish.