I stupidly set up my account under the wrong email address (… it was at a time when the service provider needed to change it coz it was so old and I got mixed up) ..which meant I never actually was able to validate the email account.

Through laziness, I've never sorted it out and as I could still use the service and wasn't expecting to buy anything (so I thought!) and so carried on regardless. However, I would like to set the link up (and realign all market place purchases) with my actual email address.

I couldn't see on the forums how to switch email address / accounts? 

I would contact Support to associate your account with a different Twitch account.  They would be able to help with the linking, I'd imagine.

That was quick! Many thanks!