In short, definitely yes!
I took a job in March 2012, in East Sussex for a firm of Chartered Accountants as an Accounts Trainee. The starting pay was £15,000 and has just been increased to £16,500 pa with my title now being Accounts Junior.
I would point out that I had no relevant accounting experience or qualifications prior to this job; I was a Uni drop-out (Sports Science) and I was previously working in Estate Agency and Recruitment, a somewhat questionable CV overall!
I am currently studying AAT Level 2 during working hours, and paid for by the company. I'm about to start studying AAT Level 3 alongside (albeit in my own time), which the company are also funding. They have expressed that they would be willing to pay for ACA/ACCA training on completion of AAT L4, and that my salary will also steadily increase during this time if I continue to perform as expected.
I do a little bit of overtime off my own initiative sometimes, but to be honest my responsibilities are not that vast. You mentioned you're expected to stay late to meet deadlines, and they also recognise that you are now AAT qualified and senior enough to mentor new recruits. It sounds like you have a lot of plates to juggle alongside your studies!
On face value I would recommend looking elsewhere, it definitely seems like more financially rewarding opportunities are out there. Having said that, money is not the be-all and end-all for everyone, I don't know what you financial commitments are...if you can live comfortably on your current salary, and enjoy working there while you are still studying, maybe it's not best to rock the boat.
If you do end up going somewhere else, how do you know if you will get along well with your new superiors/colleagues? Is the potential stress and aggro from unreasonable bosses and idiot co-workers worth an extra few thousand pounds a year?
I guess the other thing to consider is the experience you are currently getting. At the end of the day, I reckon working in practice is definitely the way forward, you're getting varied yet specific experience in exactly the right areas (I don't know if you want to end up specialising in Audit?). This is very difficult to quantify in GBP, one of the others who replied mentioned they were happy to take a bit of a hit in their initial salary as they were desperate for the experience, I can certainly relate to this, it took me a while to find this job but now I have even a little bit of experience, and have started studying, I feel getting another accounts job would be much easier than before.
Having said that it sounds like you have a fair bit more experience than me, and have done the AAT by the sounds of it, so I'm sure if you had a chat to some recruiters you could get yourself a few interviews lined up.
Maybe I was just lucky, maybe my pay reflects my age (I just turned 24).
I'd be interested to hear from others employed in similar positions, I think you mentioned you also live in the South of UK, where salaries should be slightly higher I would have thought?
Sorry for writing an essay, but considering the above points, if you were on a higher salary in your current job, would you be happy? Have you (and your several colleagues at a similar level) discussed the salary issues with your employer? If you're profitable for the company and have good relationships with the clients you deal with, they would be silly to lose you, and have to replace you with a potentially unknown quantity.
The worst they can say is no! Let us know how you get on.
Cheers,
Matt