Considering extra-European, therefore 'imperial', battles, key ones on land are Plassey (1757 - India), The Plains of Abraham (Quebec, 1759), Yorktown (Virginia, 1781), Seringapatam (India, 1799), Gujarat (India, 1849), Alexandria (Egypt, 1882 - not much of a battle, but a significant event).
In South Africa, the most famous battles (Colenso, Spion Kop, 1899-1900) were defeats for the British, who nonetheless eventually ground out victory in the war through a series of minor victories. (The Second Boer War, was I think the first in which Australia, Canada and New Zealand sent troops to fight alongside the British troops from the UK and the Cape, making it possibly the first time the battles were truly 'Empire' ones.)