Thanks for the message. As it happens, I was able to have a good conversation with the Prins agent/fitter that I visited in the North Wales area and got a lot of confidence from it; I shall visit the in the first instance, given the distances concerned -but if there's any issue, I'll get back in touch to take you up on that offer.
The car's running great on petrol - I have spent some time ironing out any problems before starting the conversion.
That being said, I'm still underway with the install - doing what I can in evenings after work or over weekends. As you suggest, the kit has worked well on another car with an identical engine. I'll put together together a quick thread on my progress elsewhere on the forum and point to it from here in a moment.