I'll try and get some pics up tomorrow.
It basically does (around) the same on LPG as it does on petrol (you usually expect 10% less power and 10% less mpg depending on the system) but the cost is less (and don't forget that petrol goes up again Jan with the VAT increase)
There are a few LPG stations on the Wirral, cheapest is Calor Gas by Lairds, but only open office hours, 24hrs are Shell Eastham and Shell Upton, both still less than 60p per litre.
I've had three (maybe four) Grand Voyagers on LPG, and the tanks are stupidly strong, when something ran into the back of one of them (the tank was underneath) the bodywork folded around it. I've had a Forester on LPG (cheap ass single point system that REALLY needed a service, back fired like you wouldn't believe) and I had a system specially fitted in a Subaru SVX with hidden pipework and filler, so I'm fairly convinced it works (and doesn't smell quite as bad as the Pajero I run on cooking oil)
You can have the systems set up pretty much how you want, when the SVX was having it's LPG computer programmed he asked what it would do top end (just over 150), he said that he could set it to deliver about 175 but it would kill the mpg lower down, or have much higher mpg but lower top end.
Most bits for a system can be changed, although, as Chris says, some of the early systems can be a pain to get parts for, although as most of the work is done changing the system is a relatively easy job and takes less than a day (if you know what you are doing, your insrance company wont like it if you use lots of gaffa tape
Distance you get with LPG basically depends on the tank, if you have a small one that goes where the spare wheel did (as I have on my Voyager) it doesn't do much to a gallon anyway so I get around 200miles. If you have a huge tank in the boot, you just fill it once a month
I "have" heard that some people have a pump to use LPG from cylinders or the home heating gas as this works out at around 15p per litre, but this does mean that revenue hasn't been paid on it and the penalities can be the same as running on red (diesel).