We're just up the hill from Charlie, and a previous curate of the parish church was keen on the idea, to the extent of volunteering the church itself rather than the hall. A member of the PCC is also a Fridays member... For a small number, our house might be possible. We're probably less than half way, which may or may not be an issue. Catering and bike security at the end might be tricky, but
@Fab Foodie had the idea of going on to Abingdon. No train, and an unglamorous destination, though.
London to Oxford was a ride I promised to put on as an experiment - a promise I have failed to keep. My mental plan was A404 to Amersham, A413 to Missenden, avoiding the horrible road surface which did for
@GrumpyGregry. Then through the hills to Risborough, Phoenix trail to Thame and via Stanton Street John to Oxford.
In an ideal world there would be parallel rides from Brum and Bristol to converge.