The weekend effect does exist to some extent, I mean in Japan the sales in the weekend always give the singles/albums a boost so I think it applies to UK and in most countries I think.

Could it partly be the reverse? A sort of Monday/Tues effect. What I mean is, is there still enough hard core chart fans checking for new releases or climbers they don't yet have each week at the beginning end of the week to boost newer stuff up at that point, with the less hyped/front loaded stuff potentially being boosted at the beginning of two or three weeks as more chart watchers pick up on those tracks.