Pat
I know exactly where Trafalgar Square is.
It is in what is now known as Southmoor, south of the A420. It's a small area just off Town Pond Lane, which itself is a lane off the Hanney Road.
If you look at Google maps you will find Town Pond Lane named.
Try OX13 5HS or see listing for properties at that postcode on Zoopla.
KN