I'm not really sure what your question is. This is the satellite box and you meantion Top Up TV, which is terrestrial. Next I guess you got your fishing in the days of ONDigital because Discovery has never been Free To Air on Freeview it has always been a TUTV subscription service.
Do you have a satellite receiver and a Sky subscription that includes the Discovery channels? If so, you need to contact Discovery and ask them about fshing programmes. If you have TUTV, it only has a subset of the Discovery channels and so to increase the number of channels, you need to install a satellite receiver and a Sky subscription that includes the Discovery channels?
t, February 2007