I have the £10 bike breakdown service for me (frequently 75km from home with only a few hexes & chaintool) and my wife (zero tech bike nouse, no desire to obtain it).

It was £10 each 'cos we have our car registered with them too (not bad compared to AA / others). They also do a pan-Europe bike breakdown for an extra £15 a year - would have been very handy in the Ardennes a few weeks back when my front mech imploded 50km from the gite with wife not happy driving Belgian motorways to rescue me (Luckily a bodge meant the ride was finishable in big ring.)

They will take you to a bikeshop, train station or hotel, or home if within 25 miles.

Has anyone used or heard of anyone using them in anger to rescue a stricken cyclist, in the UK or Europe?

I've read a conversation on the CTC forum, where they seem to prefer 'self-insuring' and getting a taxi. Which would involve: finding a taxi, finding a taxi willing to take a bike, and also the cost of getting a long way back home. Certainly overseas, a single phonecall to a UK number and then someone with you within an hour sounds awesome. Even in the UK, the idea of being miles from anywhere trying to arrange taxis etc is not good.