Thankyou for your explanations, chevron. Now I know what a Marshalling Point is/was, it doesn't really make sense that they formed part of ATC procedure at a civil licensed airfield with hard runways and taxiways, IYSWIM. I still don't get why APP would be issuing takeoff clearances from any airfield. One wonders if landing clearances were also part of the NWI APP remit.
On a side note, at Leeds Bradford some decades ago, TWR and APP (procedural) were combined on a single frequency. The RAD controller was also based in the VCR but shut away in a tiny corner with a single PPI fed from a Plessey 430. Radar was then purely for vectors and SRAs. No RAS or RIS was available. I think East Midlands (perhaps other airfields too) had a similar arrangement for a time.