Exact Production Status

As regards the role that Fox played in this series. They are here credited as co-producers of the series, but when you look at the credits for the individual movies, only four of the thirteen are credited as having been co-produced by Fox. The other nine only say Hammer. On the BFI site, it is similarly shown as a co-produced series, but all of the individual entries show only Hammer as the production company.

Also, I have a recording of Black Carrion. In the opening credits, it shows Fox as having the copyright, and in the closing credits it only shows Hammer as having produced it.

Also, the only information I can find anywhere that provides any details of Fox's involvement, suggests that Hammer produced it, and there was some sort of deal where Fox bought the distribution rights for America and that American actors were used to enhance the marketability there.

Does anyone know, for certain, if Fox did actually co-produce the series, or whether their involvement was confined to copyright and distribution arrangements?