Bare in mind that the pc you linked does not come with windows installed, you would need to add on another £100.
At that price point, if your mum is only using it for very light usage, might be more economical viable to get a pre built pc. But then again it all depends on what you can find.
If a computer is being used for only light use you will not notice higher end equipment so check out the pc world ect to see what you can find there.
( I am sure I will get murdered on here for suggesting a pre built pc)