Was the British Army (including Empire troops) well led?

They certainly weren't the worst going by casualty figures both killed and wounded.

A tiny force at the start of the war, they were the only force at the end of it capable of withstanding the massive German assault brought about by the release of over a million German troops from the former eastern front and then followed that up with an offensive of their own that brought the war to an end.

They embraced new technology quicker than any of the other combatant nations and proved themselves to be great innovators and improvisers.

So on balance I would have to side towards the argument that states they were well led.