Just an update to say that I finally did get a refund…however, this also came at a price:

“Please note that as a result of your refund, your Avast GrimeFighter - 3 users, 1 year license had been disabled, which, with regret, will stop your avast! antivirus from being updated.
The only way to rectify this issue is to purchase another license key.”

Cheers Avast. So in other words “you can have your money back, but you still have to pay :P”.