Well, it seems Vodafone really do want to kill off PAYG. £20 used to last my wife 6 months, but as of a couple of weeks ago there is a £1 a day charge even if you don't use the phone - then "unlimited" for the rest of the day. We did get advsed, but I naively assumed it only applied to days the phone was used on the network, a bit like £4 a day charge that got levied when roaming in certain countries. Gee, thanks for nothing. Up to then 90% of her usage was on the home WiFi so attracted no charges at all, hence the long life of her credit. So, time to convert her phone to a cheap SIM only contract I think. I doubt Vodafone will be the last operator to do this. Others already make you top up monthly by not rolling over PAYG credit - so a defacto contract with variable payments.
ETA: My perusing of SIM only deals, including on the Vodafone website, might have, Big Brother stylee, have born3 fruit, as an email arrived this evening, offering discounted deals to existing customers to swap from PAYG to contract, the cheapest being a £7 a month deal with 500Mb of data (wife uses virtually none) and unlimited minutes and texts. I shall check more carefully tomorrow.