Thanks for the info @Carley_S
I didn't get a receipt for the return, the member of staff at the One Stop scanned the returns box on a device (presumably Yodel device), asked me to put in my email address, I declined and the transaction was complete.
Naturally, I regret not complying and handing out my email address for tracking purposes, but I didn't want subsequent spam and marketing from Yodel and One Stop to flood into my inbox. I didn't think to use the Yodel app on my phone to scan the box myself, but I wouldn't want to install another data harvesting app on my phone neither.
I'd assumed once it had been scanned by the operator taking receipt of the package that it was in the system and VM or at least Yodel would know about it.
I'm hoping once the equipment is batch processed at VM's end that I will be refunded the £40 taken along with the remainder of credit that is on my now disconnected (on 22nd July) account.