I think you need to move WM
There is no way I would tolerate a pre payment meter. Presumably the meter belongs to SP but what would happen if you wanted to change supplier but I suppose your landlord would not allow that. At least you now have the option to keep spare batteries but perhaps the meter is sealed so that you cannot. I have changed supplier several times with the same meter, last but one with SP but soon came into conflict and changed again. Of course the gas supply is unlikely to fail unless a pipe is broken somewhere unlike electricity which can easily fail for many reasons.
Although we had bottled gas for many years I have never liked piped gas, too dangerous you only have to leave something on unlit for a while and whoosh!
I can remember as a kid, my mother in her heyday having a scrap with the Gas Board and deciding to go electric. She told them to remove the meter but they refused so on the phone I heard her say "come and take it by such and such a time or you will find it in the road" They came but lots of things were different in those days.