Girl Thing we're managed by the Spice Girls' ex-manager simon Fuller and he marketed them into the same mould as the Spices however it backfired, as both singles didn't do to well and they were dropped. Apparently Hear'Say's "Pure and Simple" was originally written for them.
Other flops that spring to mind are:
Blessed - They had a song called "Booo" which didn't chart, however they had a very laughable video where the girl members tried to dance in the road, and had a dodgy old man as the DJ.
Benefit - Bizzarely, they were big in Lebanon and Ukraine where they had a song called "Sex Sells" which was a bigger hit in Scandiniva by Finnish singer Sheidi. Their UK hit was a latino number called "What's It Gonna Be?". They are probably living up to their group namenow
D-Side - Irish boyband, who had hits with "Invisible", "Real World" and "Speechless". Shame they flopped as they had potential.
Reel - Another Irish boyband, who could be described more as Westlife meets the Corrs. Had three top 40 hits, but were HUGE in Ireland.
Skandal - All I know of these, were they were touted to be the next big thing, and were one of the for-runners of these "boybands with attitude". Their only single flopped and they appeared on the Trisha show to launch the song back in 2000.