Stuck in the 70s with the Rubettes

I have found myself stuck in the 70s this week, listening to a glam rock mix on my iPod while driving to various assignments.
One of the songs, "Sugar Baby Love" by the Rubettes, owes its success to one of the oddest stories in British pop history.
During the spring of 1974, Sparks were scheduled to appear on the BBC's "Top of the Pops" to perform "This Town Ain't Big Enough For the Both of Us." That was until TOTP producers realized Sparks were American and not British -- and thus not yet members of the Musician's Union. The Beeb scrambled to find a replacement act and happened upon the Rubettes, whose "Sugar Baby Love" was languishing in the charts with little real hope of success.
The last-minute replacements duly performed their tune and it subsequently took off.
It knocked ABBA's "Waterloo" off the top of the charts in May 1974 and held on to No. 1 for four weeks (it's successor as chart-topper? "The Streak" by Ray Stevens).
Sparks eventually reached an agreement to perform on TOTP, but "This Town..." couldn't quite equal the success of "Sugar Baby Love."