Tim came up today, and I explained the issue of the engine cap bolts coming loose. He is happy for me to effect whatever repair I want (within reason) so that all bolts can be accessed, inspected, and retorqued as required.
We had another go at bleeding the right brakes (where I had replaced the master cylinder). Based on limited testing, this seems OK. It's too cold and icy to take the plane outside to test it.