Thanks for your replies
My PACE STB is model No DI4001NC. I have a digisender gold that works (with a repeat key issue that can be a pain but isn't a massive problem - you just have to be quick pressing the buttons

).
I noticed that there is a 'remote in' socket on the back of the stb - perhaps this would be an option if the dvd player supports it, though I seem to remember from somewhere deep in my memory that this wasn't enabled.