I produce and sell pump setups that pump gas from red propane bottles into LPG converted vehicles tanks :-)
I sell the pumps for £375 + £8 shipping privately (away from Ebay that takes commision), or at £399 + £8 shipping through EBay.
To save some typing and posting pictures here I will include a link to my Ebay listing, but obviously if anyone reading this wants to buy a pump it would be better to contact me directly. https://www.ebay.co.uk/itm/326295382117
I have 47kg (92.1 litre) red propane bottles delivered to home for £79.50 exchange from a local bottled gas company, this works out at 86.4p per litre. The pump is easy to use, runs from a 12v car battery and takes around 30minutes to pump the entire contents of the 92.1L bottle into my vehicle tank. No need for a separate 12v battery, just pop the bonnet and connect the power lead to the vehicle battery.
There are still forecourts local to me that sell LPG at a fairly reasonable price (92p at a local BP station) but I more often refuel at home using one of these pumps. Morrisons used to be my usual go-to forecourt but not since MFG increased the price to £1.299 per litre.
There are pros and cons to both filling at forecourts and filling at home from a bottle. I would prefer LPG to still be widely available at a low price from forecourts but it is very convenient filling at home. If you're miles from home it's a disadvantage that the cheapest place to refuel is at home but if you have decent range on LPG it becomes less of a disadvantage, while for some people/vehicles it would be possible to take a red bottle in the luggage area and refuel anywhere. The pump can also pump from bottle to bottle (may need a different output line 'end fitting' bought from me, or could use a bottle filling adapter instead)... So could pump from a large bottle into smaller bottles at home then take some smaller bottles in the vehicle luggage area to refuel from. On my own vehicle I fitted a 2nd LPG tank, if both LPG tanks are full I have 700 miles range on LPG and the original petrol tank still fitted gives another 350 miles range... I may yet remove the petrol tank and fit another LPG tank in its place but I already have no range anxiety with 700 miles range on LPG.
I imagine in the fairly distant future if EVs become the majority of vehicles on the road forecourts selling petrol and diesel will start to close too. But if I live long enough to see EVs start to take over I imagine it will still be legal to run a vehicle with a proper engine (especially if running on LPG) and I intend on still running a vehicle with a proper engine on LPG... Just refuel at home from a red bottle. LPG continues to be the cheapest fuel to run a vehicle on, no need to pay the price of a new vehicle (or suffer the depreciation).
Like Gilbert, I'd still run on LPG if there was no saving versus running on petrol, my oil stays clean far longer when running on LPG versus petrol.
When I was rebuilding my boat engine I read quite a lot on engine builder forums, a lot of people were saying that back in the days of carburettors they'd expect to see cylinder bore cross hatching worn smooth on high mileage engines but the same engines running fuel injection instead of carbs are likely to retain the cross hatching, they attribute this to the finer fuel atomisation of fuel injection being less likely to dilute the oil film on cylinder walls. LPG is a vapour before it enters the engine and won't dilute the oil film on cylinder walls, furthermore it burns cleanly and doesn't cause as much carbon or other contaminants build up in the oil.
Filling at home from a bottle I expect there'll always be a good saving running on LPG, its main use as a fuel is for home heating customers so its price has to stay competitive in that market or the gas supply companies will go bust, they might not care much about the increasingly niche market of LPG as a road fuel but these companies will want to stay competitive in the home heating market.