Where please:Not true! We live in Kent and there are at least 2 garages within 15 miles, possibly more, that sell LPG. The closest one being Morrisons. We invariably top up there as it's the cheapest one around but we're happy to fill up wherever we happen to be if we've started on the 2nd bottle. Don't bother otherwise.
As we have Gaslow and drive up and down the A2/M2 on a regular basis and our van is stored at Rochester airport.
(Other than Shell Mackinade in Faversham or Shell MFG in Birchington as both are in the process of stopping selling autogas)