Regarding signal overlaps on MAS schemes, when I started in 1966 the lengths irrespective of speed were 200 yds for 4-aspect, 300 yds for 3-aspect and 440 yds for 2-aspect with separate 2-aspect distant signals. There were rules for increasing or decreasing lengths where the gradient was steeper than 1 in 260.
At a later date the standard was changed to 200 yds at all red signals in MAS areas, with reduction for speeds of up to 60mph. These varied from 50 yds at 15mph to 150 yds at 60mph.
Gloucester PSB was designed at the time when the standard length for the Home signal at Norton Junction would have been 300 yards as quoted above by Mike. Unless the standage length had been critical, e.g. due to a desire to run very long freights via Worcester, there would have been no justification to move the signal closer to the junction when the requirement on distance was reduced to 200 yards.