I thought I would come back to this thread and update my statement above because 1p mobile have since changed their Terms & Conditions for the better since I posted.

The change, you no longer lose your credit or get charged a monthly fee if you use the standard PAYG.

You do need to buy credit of a minimum of £10 at least once every 4 Months but as long as you do that any credit left over from previous top-up just accumulate.

Still not ideal for very low user but much better than before.

https://www.1pmobile.com/terms-and-conditions.taf