Corsa-B.uk - Vauxhall, Opel and Holden Corsa B Owners Club

hi, I have just done an engine conversion from 1.2 8v to 1.6 16v (x16xe) and all is well apart from my speedo is not showing any reading. I have tried all sorts of speedo cables and although its reading a pulse (electronic speedo) im getting nothing coming through to the dials. I have read in previous posts that it could possibly be that i have an electronic speedo readout from the gearbox (f15) but a mechanical reading ECU(dont know how to check the ecu). Anyone know if this could be the cause of my problem? If so can i just buy an ecu from a scrappie that is from an electrically driven speedo and swap it over or would the chip in the key and barrel around the ignition need changing too? Please help as i have been trying to fix this for about three months now

thanks