The Beatles walk was horrible. Avoid at all costs.

Other than that, I've thoroughly enjoyed each and every walk I've taken with them.

The pub tours are a lot of fun.

You can't really go wrong, choose according to your timing and interests. As the time gets closer I'll look at the schedule and let you know what I think.

You tip or not according to how you feel.

Yes, the tour leader buys everyone's tickets. Don't know if you can use the 2-for-1 tickets, but I would assume so if that is less than the per-person group cost. Most of the sights in London are free.

I don't remember about the train. I think you all just find seats and regroup at the destination.

Have penciled in Royal London, British Museum, Thames pub walk, and Oxford/Cotswolds for upcoming trip. Will let you know.