For reference, my salary history over my 6+ year career is as follows:
£20k->£26k->£45k->£450-£600/day
Note that I am a totally average developer, nowhere near as smart or knowledgable as a lot of the guys here on HN. I have a CS degree, barely (I got a 3rd), so that helped at the beginning, but most of my luck has been thanks to an extremely welcoming market.
If you have three years experience, you should be clearing £42k, if not £45k. I don't know much about speech impediments and how easy/hard they are to fix, but in this market, trust me, you can achieve £42k+ for fizzbuzz and a pulse.
EDIT: Modified figures in last paragraph on account of OP having three years of experience.