Thanks Glyn. Yes, I have seen the video and I even linked to it for two of the techs. I think the problem is they are just not seeing much upside to fitting someone's kit if it were to go wrong for any reason. I even told the last guy " if it's working when you install it your responsibility ends there", but they still didn't follow through.
I really understand the issue thinking back to my time in business. You essentially work using someone elses's product with all that that entails when alternatively you could be off doing a job over which you had complete control understanding the likely problems and knowing that if they occur you have at least been compensated for them.
It is a shame ,because for someone with the correct tools and a basic knowledge of wiring I suspect this would not be that difficult for them. I'll keep at it, but it's not a pressing issue.