Could be a switch fault or broken wire in circuit.
Or pump may have ceased up try switching on an internal light switch on the toilet circuit then press the flush if the light slightly dims then the pump is most likely jamed, tap it with a small hammer not too hard and not too soft. The pump is located under the toilet roll holder. Remove the holder and its case and there's the pump pull it out. Test the wire for current as well as going by the light. If you have a reading then buy new pump and splice it into the old cable using a small terminal block and waterproof tape. don't try working on the switch end unless you have to its a nose bleed job from what i've been told. I've got same problem worked on one trip but second trip it had stopped but know by light dimming that current is at the pump so bought a new pump and will be fitting it at Easter in Devon where its stored.
Bob
Bob, March 2007