When i was a member of the PGAC quite a few people had there existing ECUs remapped by JAMSPORT, at around the figure of £400 its probably the same price as a superchip but better as said before its mapped for your car. The lads who had it done swore by it and gaind aproven increace on the RR.
I had a Dastek fitted to my 106 and TBH it made next to no diference, infact i thought it was mapped crap, and made the car worse to drive, though that will have been down to who mapped it. Also not all parameters could be changed i.e.the rev limit couldnt be raised without an add-on.