In reply to Jenny C:
> Is the old PAYG where you to up every few months once your credit runs low still a thing? All I can find are monthly plans.
There are Payg options still about. Giffgaff do them (O2 network) for example.
If data is to be used, however, watch out for any contracts that have a minimum price/day for data usage. Most, if not all(?), smartphones now a days use some background data for things touching base even if you don’t actually open apps, etc., so credit will be used “silently”. A quick check for say emails once a day will soon add up with those with a min charge. Switching off mobile data though and using only Wi-Fi is what some do (consider security risks of using unsecured Wi-Fi).
Giffgaff have, I think, a min charge of 20p as minimum charge per day if any data is used. Could be cheaper to buy one of there monthly packages which can be changed monthly and credit can be used as well.