Reading and/or Abingdon gaol records

[CarolA3]

Hello Berkshire people

I've recently discovered my first convict ancestor.  Ggg-grandfather lived in Cumnor, and was imprisoned several times between 1847 and 1855.  He appeared before the magistrates and at quarter sessions, sometimes in Reading and sometimes in Abingdon.  His last sentence (12 months) was imposed on 2 January 1855 at Abingdon quarter sessions.
(Info from newspaper archives on FindMyPast.)

He died in Cumnor on 27 January 1856 - cause of death 'decline'.
(Info from death cert.)

The newspapers don't say which prison(s) he went to, but presumably Reading and/or Abingdon.  Does anyone know where I could find prisoner records from those establishments for that period?

Thanks in advance
Carol