This has been bugging me for TEN YEARS!!!!

An 80's song that was a breif hit in Australia - don't know the title but it could be 'What are you on'. Have no idea of the band name.

Only section of the chorus I can remember goes:
What are you on?
Where did you get it?
How much does(did?) it cost?

Only line from a verse I remember is:
My head feels like a boiled potatoe...

In case you haven't guessed it was a silly novelty song. The lead singer was female and the video had the band all on a roller coaster... I think!

PLEASE HELP ME!!!