Latest favourite tipple is a heady mix of a can of Abbot Ale and a (smaller) can of Mackeson. The trick is to mix them in a jug about an hour before drinking. This gives the gas a chance to escape and the temperature rise a bit.
I know it's really only black and tan, but I'd recommend it.
But make sure it's mixed. Don't go poncing about with pouring the Mackeson over the back of a spoon.
It's much more complex than Porter, tastewise.