Thanks for the reply, Busy Bee.
It occurs to me that Co-op Travel might be repackaging more than one tour operator's holidays. I based my post upon trying a dummy booking on the Co-op Travel website and seeing what information I could find out.
On the (secure) page, where you actually confirm your booking, you'll see that you're required to tick two boxes. The first of those is to indicate your agreement to the tour operator's conditions. (The second one is agreeing to Co-op Travel's conditions). If you click on where it says (something like) 'I agree to the tour operator's terms and conditions', you'll be taken to a page which lays out those conditions. The page I was taken to was packed with references to Thomson (and with links to Thomson pages). Perhaps you'll be taken to a page about Cosmos? (Give it a try!).
Enjoy your holiday. I'm still unemployed most of the time, so I don't get any real holidays but I'm off to Germany for a day out on Saturday (�12 return fare including taxes, charges, booking fees etc, with Ryanair) and I've got another day trip (to Italy) booked for a fortnight later!
Chris