Thanks for te advice.
It turned out that all that was needed was to unplug the decoder leave for a few seconds then plug in again, and all was re-set and now working fine.
But. 'My Friend' now wants to know if the crad he has, which is a Sky card marked DNS, will need to be replaced with a new card?
Any ideas please. (my friend cannot call Sky as it wil show he is not in UK)