I wouldn't recommend anyone to proceed along the lines suggested above. I dont think I'm being unkind if I describe the results as shambolic!
I'm currently left with a phone which can only accept incoming calls until such time as the attempt to move to PAYG is successfully reversed.
Not what I wanted really. The unsuccessful move to PAYG, anyhow, was motivated by a desire to activate roaming on at least one of our Virgin phones.
On this occasion, following several phone calls, I was able to reach a UK based Virgin employee who seemed remarkably well informed, and I am hopeful that all the problems affecting my Virgin phones may be resolved soon.
It would appear that Virgin rely on EE to enable roaming services and there are sometimes problems ensuring this has been done. This is, apparently, the most common cause of roaming problems.
So, my new friend on Virgin's UK staff is rolling back what changes have been made to my account and is also chasing up EE to enable roaming.