Pat,
That's logical...
Here in Australia, the government subsidises conversion of petrol vehicles to LPG - the subsidy is $2,000 (about 1,000 quid)
The price of an average conversion used to be about $1,100- 1,800.
Since the subsidy started, the average price is now $2,200- you pay now pay the firm $200, and the conversion company applies for you, and it gets the two grand from the government...
Used to be called the thimble and pea trick...