I do think the LPG calcs are very flawed as it doesn't take into account running on petrol to warm up etc. This makes it a bit more exensive but savings will still be there.
Sometimes you have to buy a car that is more sensible for whatever reason. Running costs, number of seats, amount of finance, boot space.... so on so on.
It's life and it's part of what being a 'grown up' is all about.