Rutland are extremely unhelpful, I am being polite. Having measured their cutters, which do not have any markings on them, I discovered the straight cutter is the wrong size as well.
I have been trawling through pictures of jigs being sold in the uk and discovered that Axminster Tools sell the same jig under the "UJK" brandname. The only difference is theirs is painted a lurid shade of orange. They also sell sets of cutters for 1/2 inch 1/4 inch and 8mm shanks. They have a good manual, which can be downloaded from their web site, and helpful technical staff who measured the cutters for me to check they were the correct ones. They also do a large range of guide bush adaptors, although sadly not one for my Makita 700. Needles to say I have ordered a 1/4 inch set - Wonderful. Now for some spare time to try it all out
Thanks for the replies guys. The problem with imperial vis metric is not one that only affects the USA. I belong to a model engineering club where many of the members are older than me (71) and still think in inches and use imperial tooling. Most of the clubs machine tools have imperial scales and when you try working on an old model the threads could be any one of a dozen different ones. Having been an engineer I think metric, mostly. We do a lot of young engineer training and find that many of them still think imperial, so its going to take more than one generation to get the change made and even then the old models and machine tools are not going to go away. The only answer is time, but I think it will take longer than most people realise. BUT - more importantly the spelling checker is telling me I have spelt REALISE incorrectly - NO I have spelt it CORRECTLY !!!!!!!!!!!
Have a nice day :-)