I think I've cracked it.
He has got an iPhone.
I turned off iMessages and FaceTime. Reset the network settings, turned iMessages and FaceTime back on and it seems to have picked up my old number so think it was a phone issue, not giffgaffs.
Just got to figure out how to get my messages to go...
I've recently changed my network provider to giffgaff from Three. I unlocked my iphone5 from 3
I used my PAC code from 3 and have ported my number over. However, I used the new temporary number supplied by giffgaff for a day whilst I was waiting for the transfer, and it happened last Wednesday...