Can't switch on roaming on ipad 2 with giffgaff SIM
I have a giffgaff sim in my ipad2, which is working in the UK. Roaming is enabled on the SIM and roaming can be switched on when the SIM is put into an iphone. However, in the ipad2, even with cellular data switched on and roaming switched on in settings "roaming off" is still displayed and greyed out. I have done the following to try and rectify the situation with no success. Has anyone had a similar experience or does anyone know of a fix ?
1) APN settings are set to those recommended by giffgaff, however carrier comes up as o2 on the ipad2 and not giffgaff as on the iphone. The giffgaff profile was also downloaded from the website as an additional check
2) a second working giffgaff SIM has been tried in the ipad but the result was the same.
3) The ipad has been powered off and on numerous times, a hard reset has been done, the cache in Safari has been emptied, cellular data has been switched on and off and aeroplane mode also toggled. I have also tried manual selection of carrier. None of this has had any effect.
I have noted that in the settings / general section, "mobile data number" is given as "unknown"
I was intending to take the ipad2 with me to Italy in a few weeks but there won't be much point if I can't get roaming set up. If the SIM appears to work correctly in an iphone 7 am I right in thinking that the problem must lie with the settings in the ipad2 ? I am running the latest update of IOS on the ipad 9.3.5.
Any thoughts would be gratefully received.
iPad 2 Wi-Fi + Cellular, iOS 9.3.5, Giffgaff SIM card