Hi I guess my hope from posting this thread is to find out what, if anything, you would do in my circumstances....
I swtiched broadband/phone providers in May 2017.
I realised i would lose my 10 year old email address but was ok with this and went about trying to change all online account details which used the old address before the termination date.
Then largely forgot about the old account.
In December this year my airline loyalty account was hacked.
After speaking to the airline they told me that the hacker had entered in my ID number and then used the forgotten password