Why won't they just go to bed??!

The twins are just driving us mad at the moment - they just won't go to bed! We are trying the SuperNanny advice but even that... seems like it's getting worse. Honestly! SuperNanny advises to put them to bed 15mins before their natural sleep time which is around 9pm (like i know... how late is that??!). And to bring it forward by 15mins each week, until you get to a sensible time. So tonight, we're playing with throwing paper aeroplanes and can't seem to calm it down. 'Mummy mummy look at this!'. I seriously had enough by 8:15. So we get them up the stairs, get them ready, brush teeth, calming story... threats and promises! Am back downstairs by 8:45pm. Great - target time. Can hear them mucking about. Then Abbie appears at the bottom of the stairs with her pants around her ankles and announces 'i done a poopee!'. Yep just another delaying tactic, little monkey. So i sort that out. More threats and promises. 10mins later still mucking about. Neil sneaks up there and then all hell breaks loose with screaming and crying. A huge yawn escapes during crying! And then after a cuddle, absolute bliss peace & quiet at last. 9:10pm. It's just so late, not sure how am going to continue with this tactic beyond this week never mind how long it'll take. I mean how many weeks will it be til we get to 7:30 anyway??