Heffer - just to clarify it, what AEU's Part A actually says is:
3000 hours as Operating Flight Crew of which 2500 hours must be as operating crew on an aircraft over 12.5 tonnes*
* may be varied at the discretion of the Director of Flight Operations
Which I think you'll find relates to the DirFltOps being able to vary the requirements wrt to the total hours required for command upgrade, i.e. in respect of those pilots whom have relevant & significant operational experiece, albeit gained flying light jets, e.g. such as corporate business jets.