Yes, thank you for the tip in your eBay description. It is really helpful!
If for any reason you want to change your CNG necam system yourself you will have to learn Russian, or at least learn how to translate websites via google. There is not too many people in the UK who will try to mess with the car and lpg. But there is a hellofalot of them in the countries that once were USSR. Anything can be bought online and there is millions of guides online.
I will leave you to this guy
https://www.drive2.ru/l/10276962/ who converted his Santa Fe to LPG himself that costed him something just over 400.
Yes, just front kits can be bought there for as little as 100. They will last at best 40k miles. Decent kit for a Volvo 5cyl will set you down for about 170