Hello from Leicester ;) Reading your requirements the first thing that jumps to mind is plasma cutter!

http://www.thefabricator.com/article...tting-aluminum

You lose the ability to mill but you gain massively in productivity as the plasma can cut a lot quicker.

Cheap Plasma cutters don't cut aluminium well so you need to invest in a decent machine and gases for the cutter but plasma bed's are easy to build and I'm sure quite a few people on here would build you a plasma bed at a reasonable price.

If this is a large run of the same parts cut from flat thin aluminium sheets the better way of doing this is not in house! You would have them stamped out instead which means have a custom cutter built this will cost at least £1k but how much depends on the size of the cutters.

I can link you to someone who would do this but you need to have high volume to be worth it.