When camping with vehicles we use a pair of 12V "Starter boxes" ie a 12V 17Ah battery in a bright yellow box, which cost uner £25 from Aldi.
There are many differrent types, but ours have a small light on the front for instant local lighting and 3 switchable cigarette lighter sockets into which we plug 8W flourescent fittings, which cost around £5 each.
One box will power a single tube for just under a week in August, and will easliy cover a weekend in the Winter.
OK so they are definatley not very "Bushcrafty" and quite bulky but once you have them the running costs are negligable and theym can be ready in seconds without having to fiddle around with fuel and possibly mantles.
My previous system was a number of second hand 12V Lead Acid gel batteries blagged from an alarm shop, you need a special charger but that was only around £12 from Maplins and each 7Ah battery would light a flourescent tube for an evening The down side was that it used crocodile clips and you had to start charging batteries several days before each trip so when I saw the starter boxes I didn't hesitate.
I am looking at replaing the tubes at some point with LEDs but at the moment it all works and doesn't cost anything.