have a little think about MOT's too. if your handy with the spanners then why not, you can always drop it on n off for MOT's.
If not then your gonna have a trip to the garage every time.
A decat will add about 2-5bhp realistically. Think about where your going with the car. Will it be a case of using the car every day, imo youd be better off buying some better brake pads/discs.
Much quicker point to point that way!