I have an old Android phone (Samsung Galaxy) that you’re welcome to have, and to keep.
As luck would have it, I also have a spare Three Mobile SIM with 600 mins calls and unlimited data.
Only catch: the contract on this SIM runs out on 9th March (I used it temporarily while travelling, and gave notice to cancel it when I got back to the UK).
Is this any good for your mum? If so I can meet you tomorrow to hand it over.