We have had a pixalated and multicoulered screen on start up for over 8 months Bt have sent out 7 you view boxes and a hub 2 and still happens there are no splitters to any connections and I have brought several new hdmi leads Bt are saying its my TV which is 4 months old and as can tell was happening on my old TV before its getting beyond a joke as what is the point in having a recordable box if I have to constantly reset the box
Maybe an electrical issue?
Did they change the power supply each time they changed the box?
Have you tried a different mains socket?
It could also be a faulty aerial or aerial cable.
Have you tried lowering the resolution on the BT box, it could be set at a higher resolution than your TV can handle, drop it to 720p or lower and see if the problem goes away.
Is this happening on Freeview channels, subscription channels or all channels. If just Freeview then go into the Youview box settings whilst on a Freeview channel and select TV Signal Quality
Is the pixelation appearing before any tv programme is seen?
Is it on the actual loading screen?
If so, have you tried starting it up without the aerial connected?
Do you have the "antenna out" option turned on the any of the boxes menus, this can cause problems.