Well I'm back again, just in case anybody ever stumbles over this thread wanting more ECDL information.
There is an official ECDL Foundation, established in 1997. More at ecdl.org
They work with National Operators, which in the UK is the British Computer Society - bcs.org - which oversees a range of qualifications including ECDL. BCS works with 1500 approved training centres which offer some or all of tutored courses, flexible learning, distance learning and testing. As mentioned earlier in the thread by raleighnut, the tests are invigilated, offline, 45 minute affairs taken at one of the centres. There are seven modules currently in a complete ECDL qualification.
I eventually went over to Everton Development Trust and I've been using their materials/computers and taking tests with them. They've no funding at present for ECDL, so if/when I've paid for all the materials, the tests, plus the registration with BCS I'll have coughed up £275. This is more than the couple of online providers I got in touch with (about £175 - £200 looked average), but they weren't offering the invigilated tests, so couldn't be offering genuine ECDL awards. That's not to say that they don't provide some sort of qualification, but how recognised that might be I don't know. And some of the online reviews weren't very convincing.
So far I've passed the Word and Excel modules. It's not terribly high-level, and the tutors over at EDT know their stuff. I suspect I'll have completed the whole thing within a couple more weeks.
Yes, you could pick this up easily enough if you were just using the Office suite frequently, and there's plenty of help in the various Office for Dummies books and on youtube, for example. But if that certificate looks good to a potential employer and you want to become useful with Office in a short time then ECDL might be worth looking at.