I had a prinz system fitted by
https://www.garage-gas4cars.com/ near milton keynes, it was trouble free for seven years.
I had it transferred to my current 940 by some london people.(now disappeared). Not impressed.
Unresolved fault meant it used far too much petrol (100 quid a month).
Now fully sorted by an impressive garage in Slough:
http://www.bpvservicing.co.uk/
Look at their google reviews.
it was an electrical fault which they sorted in less than an hour. I think they understand both cars and lpg...