I'd never even heard of the 5p plan until I just read the thread about the new tariffs. I had been considering the unlimited national plan as I have a son we phone in Wales, but I think the 5p tariff will be even better value as the bulk of the calls are local calls with the kids phoning their mates.
Just phoned up, first time I've phoned customer services in a while. Got through pretty quick, and spoke to a very nice girl called Amy (Scottish accent, so I guess it was Glasgow call centre). She's swapped us over to the 5p tariff, should be active in 24hrs.
If that's a typical call it should be much improved over past experience of being on hold for ages.