i use a gasit tank and i can refill it from my local garage, you can get the external filling port for it as well ( but i havent )
it costs 72 per litre to refill, and the best thing is you can just top it up when you want.
i normally fill up with deisel once a week and while im there fill up the gas.
been using it for the last couple of years, would never go back to swapping lpg cylinders
heres a pic before i fitted it
