Hi several options here, maybe first go for the DTUK pedalbox, although not a remap will give you an increase in power feel. Then there is their tuning box, which is a DIY fitment which clicks into your wiring loom and will be good for 30/40 bhp. This can then be removed if you sell the car, and i think they'll reprogram for your next car.
Then the ecu remap, good again for 30/40bhp. several options here. Had both Superchips and Revo. Superchips also do a Bluefin device which contains the same map as the ecu tune but you can pop it in and out as you want.
I've had both the Bluefin and pedalbox on a GTD at the same time and was happy with the results, although i did like the pedalbox with the standard car. Cost wise maps/tuning box £400ish and pedalbox £200.