If you listen to pick of the pops in radio 2 any chart from the late 90s on (I believe) they have to explain that records were issued, spent a week in the charts then vanished
I became very suspicious about the charts when the BBC were playing records that weren't going to be available for 2 months. The BBC itself was/is very suspect when it comes to the charts. Remember when Mathew Banister decided to axe all the old djs, he also stopped radio one playing any older bands or classic songs....he lost 5 million listeners and basically opened the door to commercial radio which is now 30 years later destroying the BBC bit by bit.
In the 1980s in one week in the charts picked at random, this week 1984, Duran Duran, Bob Marley, Phil Collins, Queen and Wham were all in the chart. I was at school with mods, punks, skinheads, I was(am) a teddy boy, we had people onto the indi scene, Reggie, pop, new wave and heavy rock