There are no vegan hotels in London that we are aware of, although Selina Camden hotel in Chalk Farm has a vegetarian restaurant on its ground floor which has some vegan options. In Central London there are many branches of Pret-a-Manger where you could purchase a light vegan breakfast.
Rooms to Let / Flat shares
If you are looking for a room to share or rent, or have a room to offer, then the following sites may be helpful:
NOTENOTE: For those not able to stay at a vegan friendly B&B, the Gallery Cafe in Bethnal Green is a vegan cafe which offers a full English vegan breakfast. Kin Cafe, a vegetarian cafe in Central London, offers vegan breakfast options. Also, one can get vegan breakfast pots from Pret A Manger and other central London locations.