Many thanks for your suggestion.
I have managed to borrow another TV , set up discovery plus on it and watched the rugby on it and it was unbelievable, no jumping whatso ever. This was in another room in my house.
So it looks like the problem lies with my original TV.
I wonder if the problem lies with the locality of the hub/router and this is interfering with the picture.
I will try and move the router as far away from the TV as possible.
Thanks for the update and for testing on another TV, @Micknal.
It's great to hear you were able to watch the rugby without any interruptions.
Let us know how you get on.
Debbie