Hmm, they're only 30 minutes from me. Problem is, the manifold is only plastic (air inlet on a Zetec) and I've contacted a similar firm who weren't interested (well, they never replied to my email). I'll give them a go...
Would prefer to do it myself but my history with straight filing is not good and I don't want to get this wrong, otherwise I'll have air gaps round the Plenum. I've got some instant gasket - will that do as well for hiding any imperfections?