Showaddywaddy began their career writing their own material and this yielded four UK top twenty hits, their debut single (Hey rock'n'roll) peaking at number two in 1974 while the next three (Rock'n'roll lady, Hey Mr Christmas, Sweet music) all peaked in the teens.
For their next single, Showaddywaddy covered Three steps to heaven (Eddie Cochran). This became their second number two hit and the first of several major hits with covers of rock'n'roll oldies, the other UK top ten hits being Heartbeat, Under the moon of love (a number one hit), When, You got what it takes, Dancing party, I wonder why, A little bit of soap and Pretty little angel eyes. After 1978, their fortunes declined gradually. They had a further eight UK hits between 1979 and 1982 but none of them made the top ten.
Critics didn't like their music at all, but the British public bought their records in vast quantities. The problem for the critics was that Showaddywaddy were something of a lightweight group who presented rock'n'roll in a semi-easy listening style. Of course this doesn't suit everybody but a lot of people didn't know the songs in their original form Some of them, including Under the moon of love, hadn't charted in Britain at all before Showaddywaddy recorded them. In any case, music is meant to be fun and that's what Showaddywaddy provided.
If you want authentic rock'n'roll, buy the original artists. If you just want entertaining music that sounds like rock'n'roll, you might enjoy the music of Showaddywaddy. While I generally prefer the original stuff, I like Showaddywaddy too.