How about Australia announces the selection of the Vigilante in late 1963 and is still in the process of determining the exact configuration of the aircraft when it becomes apparent to the RAF and British industry that the TSR2 is living on borrowed time. The RAF becomes desperate to find a backup plan that is not the Blackburn Buccaneer and British industry is looking for anything that isn't a US built F-111 with hardly any local content, Australia's earlier decision appears to offer a solution.
End result is a minimum change but Anglicised A-5B, using systems from the TSR2 and Buccaneer, assembled in the UK and Australia from a mix of UK and Australian components, as well as carry over US assemblies.