Have you had a go with a sink plunger? Otherwise you can buy some stuff from the hardware shop I think it's called caustic soda which is massively toxic & can burn skin if you're not v careful but is v. effective at clearing blocked drains. If I were you I'd pour the c.soda down the shower drain but if you have littlies ensure that the bathroom door is secured from the outside. You should prob. do it overnight.
the drain has a hair catcher thingy and i am always clearing that out - will invest in plunger then get drain cleaner stuff - caustic soda sounds lethal but will go there as a last resort -- thanks loads