I had a great stay at the house of John and Fiona. They are warm and welcoming. On the first day, John showed me Gunnersbury. The location is really near to tube connections and trains. The room is big and clean. There is access to the washing mashine and a own fridge. The kitchen is also accessible everytime you like.
Of course, a stay in London is expensive, but even though to stay with Fiona and John is a good opportunity.
Wish you all the Best!
Bettina