Yes, their garage used to be located at the bottom of Swalwell Bank, next door to Fewsters.

I think they also had some arrangement with Thirlwell Coaches located further on up Swalwell Bank. Sometimes, you used to see Thirlwell Coaches in Derwent's yard and sometimes they ran the school services.

There were two bus stations/drop off points at the National Garden Festival. There was the coach drop off at the CWS Flour Mill on St Omers Road (as you described), but there was also the commercial bus station located at the Teams where the X66 turns into before running along the bus-only section of route along the riverside. There was also Jetty located there as a ferry ran between the Quayside and the Festival.