As far as I was aware, FMP has Parish Transcripts as well as BT's. Perhaps I'm mistaken. Also, Bt's are used quite widely in Anc. When I compare those with my PR CD's for Bucks, they also contain the same BT's, where PR's fail to exist, or are lost/destroyed.
What Parishes in Berks Ben,?.....there are a few that are included in Oxfordshire. I have some, but not many for Berks.