'So Long' did indeed not make the Top 50 - but it definitely featured on TOTP as a new release. There are clips on Youtube - it really did happen, Tortfeasor, I remember it!
Yes - I have seen it on Youtube before - but never knew it was actually shown on the actual TV episode of TOTP!!
- I wish we could see all of the TOTP episodes from 1974 onwards with all these Abba appearances and more - but this seems unlikely what with all the continuing DLT/Savile commotion!
When will we find out about DLT?