Well, a fair amount of my internet research hasn't paid off. It seems many of the churches that were listed as having a weekly Solemn High Mass are only having Low Mass instead. There are many, many beautiful Catholic churches here in London, as well as beautiful Anglican churches - like the ones I visit when ringing bells.
Since St. James Spanish Place was only going to be Low Mass, I decided to go ringing. I started out at St. Mary Abbots and got to ring some Grandsire Caters (9 bell method). The ringers were then going to two more churches to ring their bells for services. Many London churches do not have regular bell ringers, nor any significant numbers of parishioners who are ringers. The ringing is left to members of three or four groups of hobbyists.
The next church was St. Luke in Chelsea, and I rang a bit more Grandsire Caters. They are raising money to re-cast and re-hang the bells. They are a bit difficult to ring.
And then to St. Stephen, Rochester Row, where I rang some Stedman Triples (7 bell method). Their bells have been rehung, and are very nice to ring. The pendulum of the steeple clock swings in the middle of the ringing room.
Then I walked back to my room through Kensington Park, behind Kensington Palace.
Then just a short rest before late afternoon and evening places.