They've marked mine up as 'Low Pressure Gas'
Now you have to be very careful here. Your Policy document forms part of the contract between you and the insurer and you have a responsibility to inform the insurer if there is anything in the policy that is not correct. Even if it's a typo. (And the reverse is also the case). So I would call them and inform them that your policy says Low Pressure Gas when it is in fact Liquid Petroleum Gas. If they say that's OK, then it's fine (and just different terms being used) but make a note of the date and time of your call and who you spoke to so that in the event of any come back you have a defence.
Remember, it is in all insurance company's best interests not to pay out, so they will use any wiggle room they can.
Proud to have a "Gas Guzzler"