Hmmm £100 sounds gd, but £150-180 does sound expensive. Thing is my cars is on Lease hire so not sure if its really worth it as ill be giving the car back to the Stealer in September 2016. The acceleration lag does annoy me quite a lot though. God only knows what was wrong with the good old fashioned cable operated accelerator 
Emission control is the reason.
If you ask for Andrew (the owners) when you phone DTUK he may do a deal. Ive known him for years as he grew up living in the house next to my workshop garage.