There's two rings in London that could accommodate you and an opponent if you find one - Walthamstow ring is ideal, huge space, decent sized ring, shower/changing facilities, run by a woman wrestler. SE9 Mottingham venue has a good ring, but tight space, no facilities, but still a very good venue.
Be happy to sponsor the rooms, and find you a suitable opponent if you havent so far.
Regards
Gus