Could I be refused exit at Bracknell because I've paid for a cheaper ticket?
Hi, ConHill and welcome to the forum.
I believe that the answer is "yes, you could be refused exit at Bracknell since that station is not on any of the acceptable routes from Bristol to Blackwater" ... and indeed you'll be travelling without a valid ticket (and subject to any penalties that may apply) between Wokingham and Bracknell.
Frustrating, I'm sure
... I used to have a "St Mary Cray OR Petts Wood to London" season ticket to allow for such eventualities, and to let me choose whichever south London terminus I wanted to use. Is any such scheme available to help ConHill?