OK. 1 x television + 1 x standard but elderly Sky box + 1 x SCART. In reality the setup is more complex but let's reduce it to the basics to save confusion. Everything has worked fine for years, perfect picture, no problems, until all of a sudden last week the picture started doing this kind of impressive trick:

A sort of flicker, unnoticeable for much of the time but exacerbated by bright pictures. No other interference present. Replacing the digibox with a DVD player replicates the problem, therefore proving the issue either to the TV or the SCART.
So, is anyone able to shed any light on how to solve this increasingly irritating problem:
1. Would a loose SCART socket in the back of the TV cause this kind of symptom? The case against would be that I can replicate the issue using both SCART 1 and SCART 2 sockets, plus the problem only suddenly occurred.
2. Would a cheap SCART lead cause this kind of symptom, again bearing in mind the problem suddenly occurred? I've also replicated the problem using five different SCART leads of middle-of-the-road quality, and don't particularly want to shell out on a super impressive one if it's not a guaranteed fix.
3. Are there any other elements that would cause this type of issue? The Sky box and TV settings are correct (RGB on, SCART control on) and the picture settings have been suitably played with.
It feels that short of buying an expensive SCART lead I've eliminated each potential cause. In this time of the credit crunch I do not want to buy anything too expensive to replace food. I'm just wondering whether any of you good people have had similar experiences or know of any tips and tricks.