I made $40k (£26k) as a raw recruit, straight out of college, as a Java developer. I got bumped to $60k (£39k) the next year. Granted, this was before the dot-com bubble collapse of the early 2000s, and in a large US city, but considering 2-3% annual inflation and that Manchester is still the 2nd largest metropolis in the UK by population and 3rd largest by money, someone like OP should probably be looking for £45k per year with a software-relevant bachelor's degree, and £40k without. Jobs likely plateau around £60k there for more experienced developers, compared with £90k+ in London.
(I am not at all familiar with the European software labor market, so all this is based on the assumption that London is equivalent to New York City and Manchester equivalent to Chicago.)
In London, those top-paying jobs will mostly be in the financial industry and the internationals that only dip their toes into the "alpha" cities. PHP folks won't ever get that high, but the talent vacuum at the upper end will sort of pull up the salaries at the lower end, right along with the cost of living.
Avoid recruitment agencies wherever you can. In the US, they have never helped me one tiny little bit, and have wasted more of my time than I care to consider. And as the original poster has noted, they made a pretty bad match.
I think it very likely that OP should be able to find a better job, at higher pay, within eight weeks. But the search process is exhausting and stressful, and full of stupid hoops to jump through. Seekers are sorely tempted to let other people handle most of the leg work for them. Don't succumb. There's no one else on Earth that will be as invested in the decision to take a new job as the person who will actually be doing the work.
I wouldn't quit today. I would use the fact that I had a job to take the time to make a better decision this time around, and to be more selective with the advertisements, applications, and interviews. With a competitive offer in your back pocket, you can then have a conversation with your current bosses with greater confidence, knowing that they no longer have the power to keep you from making rent.
Edit: Note that the target numbers above are reasonable for your first offer in the salary negotiation, or the upper end of any salary range posted with an advertisement. The actual salary will likely end up less than that, but there is always the possibility that the company agrees to give you what you ask for.
26k is below average full time wage I think. That's 27k. For a developer with 3 years experience to be earning less is not good. Its more inline with 1 year experience.
Developers should be inline with other high paid professionals.
Thanks for your advice, I'm not really familiar with UK market since I just moved to UK a year ago, so you are probably right.
My next plan will be to find some remote works. hopefully I can find some time to work my personal projects as well.
