Thank you Nigelp. This is immensely helpful and I now see the extent of Cambridge Terrace, much more than I had realised.
So I think I am right in saying that the old Cambridge Terrace would be on the left hand side of the road (today's Sussex Gardens) as you face the Edgware Road?
The person who lived there was only there in 1936 and rented a room so wouldn't be around in 1938. She writes of it: We went room hunting ... finally we found a really nice room in decent surroundings with breakfast and daily bath, running warm and cold water, relative quiet, good light, clean and decent furnishings with a couch and pull out table for 25 shillings per week...."
She gives the address as 36 Cambridge Terrace, Cumberland House, London W2
I really apprciate the help you have given me.