I agree, and I think erosion of pay differentials is happening in all sorts of sectors.
When I started with my current employer (not for profit sector) 17 years ago, I was getting 2.5 x NMW. Since then, I have had 2 promotions and am now at a level 3 grades higher than when I started, but am only getting 1.5 x NMW.
Similar roles in other sectors are paying 25%-35% more. We've lost 2 valued and experienced colleagues in the last year, who would never have left if they hadn't needed the money. It has been impossible to replace them with experienced people, so the role has effectively become a trainee post.
If I was younger, I wouldn't be hanging around either, but I'm semi-retired, part-time and can pretty much please myself re hours etc, and in all respects other than pay, the organisation is fantastic to work for. We're awaiting the outcome of a benchmarking exercise, so regrading is a possibility.
We haven't yet heard about a pay award this year, but we know it won't be much because all our projects are funded by health or social care money, and there's not a lot of that around.
If our salaries had gone up in line with NMW, my full-time colleagues would be on over £50k a year.
I think you should look elsewhere OP, you've been treated really shoddily and if my area is anything to go by, there are plenty of jobs in hospitality atm.