Not done the syringe test yet but just been down a local machining shop.

A 1mm skim they have quoted me £96 inc for both heads, a bit steep but got another couple of places to try yet.

Heavily leaning towards the 1mm slice, but only thing I'm concerned about now is by how much it will throw the cams out of sync from the original position and also each other... It will only be marginal but wondering if its worth getting the pulleys re-machined to compensate or just slap them on and see how I get on? :-/ Probably the latter as pointless spending too much for a test build I suppose.