UC migration, how to change temporary email address I added

HELP I help my son with his paperwork, he's now 31. I went through to the UC website last night and foolishly used my own email to set it all up. But there are a few questions he needs to answer himself, i.e. his bank details etc.

Can this email address be changed BEFORE completing the form in full and sending the online form off?

To be honest I have been looking after my son's paperwork for the last 12 years since his diagnosis at 19 when he was out of it to be honest, and it's continued that way. But I have had enough now and I think it's time for him to start doing this for himself.

I just cannot do this anymore. I'm worn out, exhausted, and ill myself without having to do all his stuff whilst he buries his head in the sand. I'm just too old for this now. It's too stressful by far and creates strife and angst.

I also used my own mobile phone number as he doesn't even bother to keep his mobile phone updated with any credit at all. I'm at the end of my rope here. Feeling very anxious.

Only just seen this thank you David. I shall ring CAB tomorrow and update here with any information.

Update 23rd April, I just telephoned Citizens Advice, they had no idea how to do this and told me to phone Universal Credit, or suggested their dedicated 'Help to Claim' number 08000 241 220. I rang the general number waited 53 minutes for an answer and ... onwards.