Thanks for the reply.
I understand that's usually the case where the T&Cs say something along the lines of
'contract isn't formed until the items are shipped'.
But in my case their T&C are pretty clear on that a contract has been formed as soon as the money has been taken and order confirmed.
Having done a bit of reading looks like a small claims court for 'loss of bargain' is the only approach if my initial approach by email fails.
But any info is from before the latest consumer regulations came into force so not sure if that changed anything