Yes you can get your old user name back, as you know in your profile it will not let you change your name because it keeps saying that your current email is already in use with the name LAPIII.
So what you have to do is go into your profile and you will see a option that says you can change your email address, so change your email address by just making something up like > Detfor@bob8875.yahoo.co.uk, then press submit,
You will then get a message saying that a email as been sent from toms hardware to this email Detfor@bob8875.yahoo.co.uk to confirm your account,
This will now free your own email up from Toms hardware so that you can rejoin by making a new account with the User name Advice Pro.
HOPE THIS HELPS.