This thread idea is fab. Would be great to have this for areas across Europe!
My nomination for a good hotel in
London is the Citadine chain - specifically at Barbican and Holborn. Citadines are 'apartment/hotels' so they are more like studio flats than hotel rooms. E.g. They have a mini-kitchen so you can make your own coffee, breakfast. Some of the rooms have sofa beds which may or may not be a good thing depending on your circumstances.
My mother has stayed there 2 times now and it's perfect for her, particualry the Barbican one. It's quiet on weekends, walking distance to St Pauls and safe. It is a bit more expensive than some of the other hotels people have mentioned, but in my mind it's the kind of place you'd put your Mom.... A perfect 3 star. If I recall, the rates are around £80-£90 per night, but do check online to confirm.
Also, you can book online with them and they have a
no charge for cancellation policy. [In fact that might be somethign to discuss b/c i think that is an EU or UK standard so it takes a lot of risk out of booking early]..
http://www.citadines.com/ukindex0.htmMimsy2000
(no. i'm not a citadines shareholder
)