This question has been stuck in my head since I saw your post, and it could well be there were no (or at least only few) 2A BSOs in Regional livery. I think the stock in the North West were ex BFK reclassified as BSKs in the 35xxx series, mostly ex NSE stock from the Thames and West England routes.
It could well be that the only 2A BSOs were the Scottish sets with Reggie colours and 'SCOTRAIL' branding. Although, Transpennine did have at least one 2A BSO in their house colours, so that must have gone somewhere after the TP loco hauled stopped in 1991.
My Platform 5s are still boxed after moving house, but I did come across this site about North Wales stock.
http://www.nwrail.org.uk/nwcoach.htm
Edit: Found the 1995 Platform 5.
It says there were x10 2a BSO, x1 2c BSO and x7 2a BSK (ex BFK) in Regional Railways all at Liverpool.
Inverness has x3 2a BSOT (vac braked) in Regional 'SCOTRAIL'.
So, plenty of reason for Farish to make the BSO, perhaps aong with some more of the TSOs as well.