Requested a cost using there quick quote facility and got this back:

Thank you for your e-mail. Sorry it took me more than a day to respond.
Your inquiry has been dealt with by most recommended lpg fitting centre, factory trained direct importers of AC STAG lpg systems.
Our quotes are based on the BHP and the torque of the engine as the lpg system needs to cope with fuel demand at any fuel mapping point.
Our demonstration car to prove that running on lpg does not mean loss of power is a Mercedes AMG E55 Kompressor delivering 476 BHP and 700 Nm or torque.
Our price to supply and fit Premium lpg conversion for Range Rover Vogue 4.4 is £1399.00 + vat.
The above price includes LPG KIT required to cope with BHP and torque for your vehicle. It also covers workmanship for- Lifetime – with unlimited mileage for your peace of mind and many years of happy motoring.
We offer country-wide pick-up and delivery service at no charge. Only fuel needs to be paid for. There is a free of charge courtesy car available, and the job usually takes two-three days to complete.

So - £1399 plus VAT. So it's £1678.8
Anyone got a better price from them lately? 2003 4.4 V8 Vogue
Added Tow Bar, Reversing Camera, Freeview box