The pay for signallers is roughly 19k - 37k depending on grade.
This is the important thing, there is a world of difference between a crossing keepers job and an IECC controlling stations with 500-1500 trains a day.
As a rough rule
Grade 1: Small crossing box - controls level crossings only, usually with "slots" to release a controlling boxes signals.
Grade 2: Large crossing box, very small mechanical box.
Grade 3: Small mechanical box or panel, usually passing only.
Grade 4/5: Larger mechanical boxes, with some regulating or small panel.
Grade 6: Smaller PSBs or quieter workstations, can cover some large areas. Moderate number of posts.
Grade 7: Medium sized PSBs and IECCs, reasonable number of posts.
Grade 8: and above, the busiest workstations and panels in the busiest centres. Not many of these jobs exist and there is a lot of competition is some areas to get into them. Can earn up to 50k with overtime, but it's highly likely to take quite a few years to get into these jobs and are very high pressure.