Hi Paul, welcome to the forum.
The UKBA website you have listed is correct and is the latest one valid from 18 July 2011
Cambridge ESOL tests and both the test centres mentioned (CIE & British Council) are fine. I'm not sure the cost is as much as P15k, I think around P7k - P8k is more common.
IELTS would also be valid as long as it's completed at the test centres on the UKBA approved listing.
IELTS is actually at a slightly higher level, but as long as you wife is already pretty good at English then IELTS would be no problem.
If you wife struggles a little with her English she may find IELTS a bit too tricky and stretching. Quite a few on here did IELTS.
Why not give the British Council a call and discuss.
