Yes - it was built for / by the Methodist church. Your great grandmother must have been one of the earliest students as it was built around 1851. By all accounts it was a grand looking 'campus', set within sight and sound of Big Ben. I'm currently reading a book about it 'The Story of Westminster College 1851-1951' by F. C. Pritchard M.A., Ph. D - published for Westminster College, London by The Epworth Press in 1951. If you live in the UK, see if you can get hold of a copy. Let me know how you get on.
Fliss
