Took a trip out to investigate our local bRAS building.
BT Wholesale has ten 20/21CN bRAS which are located at Birmingham, Bletchley (MK), Ealing, Edinburgh, Ilford, Kingston, Manchester, Reading, Sheffield, Faraday. If your ISP uses BT Wholesale for routing then you can be sure that all your traffic will have passed through one of the above bRAS locations.
There are a large number of network companies present at this site as indicated by the network chamber covers outside in the street.