I havent had time to check anything else Gel, this is CBeebiesHD on Virgin - I noticed this this morning for the first time. Never bothered looking before.
If you look hard enough you will find at least one fault with everty tv - normally more than 1 - none of them are perfect. There are other far worse like DSE etc
I dont think yours is a fault - if that is all you have noticed in 8 months of ownership and use then I think your doing ok - you might swop the set out and have more obvious problems and flaws with the new one.
If it was doing it in every channel on sky I would say maybe but if its only certain channels its the channels - faults are consistent or sometimes intermittent - but if it was intermittent you would get it randomly with all content, not just the same channels all the time