I live in Annan but work in Carlisle so i use both G4WHA and GM4WHA with the relevant suffixes. I have on occasions started a QSO as GM4WHA/M and changed to G4WHA/M once i join the motorway at Gretna and vice versa. When operating from inside work i use /A and if operating HF from the car at work i use /M and /P if i operate 5mhz from the car.
Geoff GM4WHA
Nonsense.
ISTR you have usefully given me two unique QSOs this way when I have been struggling to get the 4 when activating in the Northern Lakes with a handheld!
Because it was G/WB-001
And if you stand with one leg either side of the border which RSL do you use ?
Whichever one the feedpoint of the antenna is in.
OK then, a survey found a higher point than the previously accepted summit and so the location of the highest point was adopted for SOTA and it happened to be just over the border which runs along the ridge.
No, not that. Re-read your post 
Yes, I mean the fact that the southern section of the “M74” is designated A74(M) and the northern section M74. Whatever the historical reason for this, if it’s all motorway standard [which it is], it would be less confusing for travellers if it had one name.
There’s precedence for that (i.e. A1, London to Edinburgh) but perhaps national pride was at stake.
Ah, thanks for that, I was wondering what happened to WB-001…
They just listen to the GPS voice and do what it says nowadays. They don’t care what the road is called.
I prefer listening to Sally Traffic 
Yep! We are all being infantilized by letting AI navigate for us - yet another insidious loss of a human skill, map reading & route planning.
We all do it for convenience but sometimes the Sat Nav gets it wrong. On my way to a SOTA activation it directed me along an undrivable section of the Pennine Way. Its algorithm is definitely not optimized for the network of narrow, often single-track, lanes in G/LD land. Its ‘short cuts’ usually take longer to drive and are definitely more stressful than taking the slightly longer route sticking to the ‘A’ and ‘B’ roads.
Why not - they are not part of the callsign on the licence document.
73,
Rod
Happens to me when I’m back at the home QTH after an outing up north. 
… or better MM6 to keep it clear? 
73, DIZ
Only north of the border, south it would be ME6. 
During the Cold War, they were more worried about being unable to track down foreign spies’ radio transmissions, which may have become hard to detect if there had been a free-for-all all on the bands. If you think that is a bit of a joke then swallow this, today there are over 20,000 Chinese intelligence operatives (UK nationals mainly) attempting to spy for the Chinese and gain both economic and defence secrets.
And they’re not using HF radio to submit their reports.
No, not these days, it is all cyber or dead drops
An interesting approach from the RSGBCC in their recently released summary of amendments:
We will require entrants to use a callsign which correctly defines which DXCC country they are operating from. So - for example - a station operating from Scotland cannot omit the M' or S’ RSL.