removing the ecu is no big deal, it hasnt got any memory or anythign so it wont loose any settings. just unplug it, put to 1 side then plug it back in when you're done. take out the whole ecu tray, theres a plastic nut in the front passenger side corner, then you give it a good shove backwards to release the clips. then its a case of squeezing it out, bit of a tight fit.
its more liekly to be the bonnet pull cable tho, so give it a smear with a load of grease all the way round to seal up any cracks. if that helps look into buying a new one later. if it doesnt help, it might be the blanking plate under the ecu. there is a big plate stuck down over the LHD fresh air blower hole, the sealnt may have gone or some rust may be creeping in
