Perhaps some recollections of my experience of about 18 ex-GWR boxes on BR Western Region in the 1960s might be helpful. These included ground shunt disc arrangements of both probable pure GWR origin, and of the BR era incorporating some later ideas.
It appeared to me that latter GW practice was for each disc located at a point end to normally only be operable for movements diverging through those points.
'Yellow' discs have been mentioned : These were one solution to the logically problematic situation of movements legitimately needing to pass over disc-protected points while they were in their Normal position (usually the 'straight' or non-divergent) while the red exit disc was still in the 'On' (Danger, or stop) position. This was most usually in sidings where the points were an exit to the 'main' line but the siding also continued beyond the points.
As said, 'yellow' discs (yellow bar on the face and yellow 'On' night indication, instead of red) AFAIK, on the Western Region, were a later BR-era development.
Where different box-worked point ends were located near each other (e.g. along a running line, a crossover to the other line and points into a siding being closely adjacent), this could result in each point end having its own disc.
As 'yellow' discs were not normally found on running lines, this could mean that a movement to diverge at the second point had to pass the first disc in the 'On' position (i.e. at Danger). On BR(WR) in some cases such a 'first' disc was not fitted with a red glass, so it's night-time 'On' indication was white instead, but in daylight there was nothing to differentiate a 'white' red disc from one which ought never to be passed while 'On', and traincrew's route knowledge was the only way they knew which red discs could be passed while 'On' and which should not.
But where the need to shunt through running line points -
- to two or more routes, or
- it was important for staff to know to which route they were being signalled, or
- was over points in either position (Reverse or Normal),
was frequent, then by the BR period (& before?) many places had multiple-disc signals as a single unit, for as many routes as were needed; the discs being mounted vertically above one another, often up to three in number, possibly more.
Latterly, almost certainly during the BR period, at some layouts (e.g. Weston-Super-Mare, where signalling was modified in the 1950s) where necessary single discs were made able to be cleared for two or more routes, with the nearest points in either position.
So, if you want to take this kind of detail into account for your disc installations GWR_Express, you might want to decide approximately what time period that you're modelling.
Incidentally, regarding -
GWR_Express wrote: " .... confirm that my thinking is correct where in relation to the point would the signal be sited? .... "
, if you're asking, apart from 'left' or 'right' (it was not uncommon for siding exit discs to be on the right, by the way), how near their points that discs should be sited, those with the older type of detector of a rod coming directly from the point's switch toe ('blade' end) across into the base of the disc signal, then of course the disc was right beside the point toes. but the later type of detector mechanism with slides at right angles, did not need the disc to be particularly close, and they were often then something like 10 feet on the approach side of the points.