Like others have said, try Cylume Chemlights, 8 or 12 hr type. It's not like a flashlight or a flare, but it's plenty good for what it is - a marker, usually. Have had them work (dimmer, but still light good enough to read by) the second night too, and I keep a couple in the car and in my rucksack in case I get stuck out. They can also be used in lieu of a lamp in camp at night, no need to waste your torch batteries or cart around a gas lantern then. Not tried the 5 or 30 min type, but I'm not sure what sort of use they are aimed at?
I've also seen the mini glowsticks, about an inch or two long. Experimented with cracking one and leaving it inside my mapcase for an illuminated mapsheet set up, but it didn't really put out enough light. Have seen them used on fishing lures at depth by others though, with not disappointing results.
I didn't realise Krill lights were still available in the UK, where did you find one? I know SOF used to have them in but looked the other week and couldn't find a thing.