Hi
@AnthonyExmouth and welcome to the forum.
What a lovely idea to get your mum a better sewing machine. You mention that your Mum gets flustered by anything new so rather than try to pick a machine for her, she might like to try a few and see what she likes. Going by your user name, Exeter Sewing Machine Company may not be too far from you. (I’ve found them very good when I’ve ordered threads and other supplies, but I’ve not bought a machine from them.)
https://www.exetersewing.co.uk/I’m sure other forum members may know of other shops in your area. If you are able to get to a shop, they will be able to go through the features of the machines with your mum. Shops may also have second hand machines that they have taken in as part exchange. These are likely to be serviced and can be good value.
Your mum might be familiar with Singer sewing machines, but the current machines don’t have the same reputation as the older models.