@hastalavista, I am not the OP but as this is an old thread OP may not see it, so I thought I would reply.
First, you will have to do a three year doctorate. This is funded with a tax free bursary, currently £16,390 if your university is in London. In Years 2-3 you may be able to get a salaried training position, but these are rarer than they should be. If so, you will be paid on the Soulbury scale for Trainee Educational Psychologists.
Once qualified, if you work in a Local Authority then you will be paid on Scale A of the Soulbury scale. Pay ranges from points 1-6, 2-7, or 3-8. You will find it on the job advert. More services are offering 3-8 to try to attract candidates, as so many services are understaffed. Every September you will go up a point, until you reach the top of your range. (also, don't be afraid to negotiate your starting salary - you don't have to start at points 1, 2 or 3). There is a small London additional weighting.
Currently (we are waiting to find out what our Sept 2022 pay increase will be):
A1 = 38,865
A2 = 40, 838
A3 = 42, 811
A4 = 44,782
A5 = 46,755
You can Google to find out the full range, and what London weighting would be.
Once you get to the top of your A range, that's what you stay on (barring small ~1% yearly increases) unless/until you go for a promotion to a Senior EP role. Then you will be paid on Scale B of the Soulbury scale.
Finally, you can achieve up to three professional SPA points - each one of these is worth another step up the scale. Although there are guidelines for when in your career these are available and what you have to evidence, each LA sets its own rules. (for example, some services let you apply for SPA1 immediately upon graduation, some make you wait two years. Some let you apply for SPa1 and 2 at the same time, etc.) This is why Scale A goes up to point 11, because in theory you could get to the top of your pay scale (if employed on 3-8), and then have 3 SPA points, so 8+3 = 11.