It just goes to show how hard it is to advise when you don't know the area.
On paper to me, the Byron Square property looks to be in a much nicer area and the layout much more suitable, with a ground floor bedroom and shower room for your Mum, which might be sensible if she might find stairs tricky in the future. Smells and decor can easily be rectified, so can lighting.
I don't like the look of the Foster Road property because the garden is almost all in shadow and the next door loft extension is massive and overly imposing. There's also only one bathroom which is upstairs.
If it's you, DP, a DC and your Mum living together, a downstairs room for her gives you all a bit of separation as well as being future proof depending on her age and needs.
All that said, if a seemingly nicer semi is £10,000 cheaper asking price than a mid terrace, then you do have to wonder why.
One thing really puzzles me, one side the solar panels are all over the front of the roof and the other side they're all at the back. Anyone know why?