Can someone tell me how to remove the rear bumper on my Fabia lI Estate so I can check the connections to the parking sensors?

This may help

http://www.briskoda.net/forums/topic/223019-removing-rear-weights-mk2-fabia-vrs-tsi-hatch-guide/

If that don't work search for thread entitled 'removing rear weights'

This is for the hatch but the principle would likely be similar