Cliff Hercules gavee United a great start with a fine headed goal after just 7 minutes, but City levelled through Fuller after 12 minutes. Lee Cook and Kieran Gallagher then went close, but United's chances of cup progress took a jolt just before the break when Hercules was sent off for a tackle from behind on Berquez near the halfway line.
Wayne Stemp had to be replaced at the interval and United were forced to start the second half with two midfielders at the back. City's scorer Fuller made it ten men apiece 12 minutes into the second half for a foul on Stuart Beevor, being shown his second yellow card.
On 66 minutes City took the lead when Beevor failed to cut out a through ball, Bramble latched onto it and rounded Gary Phillips to score.
Gallagher wasted a great chance from close range and City keeper Catley made a good save from an Ian King free kick, but on 79 minutes City put the result beyond doubt. Jon Underwood and sub Danny Gordon failed to close down Bramble who had time to turn and fire a low shot past Phillips.
To complete United's misery, they were reduced to nine players later on, Beevor getting his marching orders for an elbow on City hero Bramble and out came the red card for the third time of the afternoon.