It costs about £75 iirc. If its just injectors you need cleaning, MrInjector has been getting very good reviews. Post your injectors off to him, you get pre cleaning report (pattern and flow rate), they are then sonically cleaned, and a report on pattern, and % increase in flow rate afterwards. He then posts them back to you all in very good time.
Everyone I know who has had it done reports great results in performance, throttle response and MPG. I remember when it was originally posted on here after the episode though, and everyone was a little sceptical. If it really was as good as they make out, far more people would be doing it as its now been available for almost two years!