I don't subscribe to the UK definitive collection but I do have the Marvel Fact Files distributed to me via Bissett. I recently sent them an email to find out when I would be receiving my next shipment and received the following email response:

Hi Stud Muffin,

Thanks for your email.

Bissett have stopped trading recently and we are due to take over their subscriptions from them but don't have an eta as to when at this time although it should be sometime soon.

We will be in touch with any information and keep an eye out for updates.

Kind regards
Joshua

Customer Experience Department
Data Base Factory - Unit 4 Pullman Business Park, Ringwood BH24 1HD
Email: Customer-Service-Australia@eaglemoss-service.com