Visiting London and can't decide what to buy tickets to

Hi everyone! My boyfriend and I are heading to London in late September and we've already booked a walking tour, tickets to a concert, and tickets to Book of Mormon. Now I'm trying to decide what other sights to buy entry to. I feel like there are SO many things that we'll obviously go to see the outside of, but I don't know if it's worth paying to go into.

On my list are: -London Eye -Tower Bridge -Tower of London -St. Paul's -Buckingham -Westminster Abbey

It's probably not feasibly (for both time and money reasons) to buy tickets to go in all these places. So I was hoping someone had insight if some were more worth it than others.

Thanks!