I did many interviews in my previous workplace, and we never cared about age when recruiting. My colleagues were between 20-something and up to retirement age (I'm now in my late twenties).
The most exciting and valuable people I've worked with were the latter. The more senior people always brought a ton of knowledge to the table and were often able to draw parallels between the stuff we were solving now with things they had already solved 20 or 30 years ago. I would not worry about your age, and your troublesome past adds some spice and a different perspective to life, and I'm sure most companies will embrace your talent.
Feel free to send me a note on chris *at** dataespresso *dot** com, and I can share with you some info about my previous employer and possibly make an introduction. They have offices all over the UK, and I think you'd enjoy working there.