Thanks for the reply guys are you ready for the story :s here goes
After two hours spent chasing the fish round the aqarium and getting very angry I floated a clear sandwich bag and with my girlfriend help guided it into the bag, one of my platys seemed pregnant a while back
But suddenly went skinny and thought she must of lost them however when cleaning out my filter I found two fry so popped them in the birthing divider aswell,
Anyway after switching the lights off all I could hear was a banging noise as the platys was pushing against the divider trying to get to the flakes below, I couldn't just pull the divider up so had to seperate all the fish into the jug but when pouring the fry and platys back in she popped out into the main tank face palm!!! So she is know back in the tank I think I'm going to leave her there and try save as many fry as possible once she gives birth!!