Has to be
'wott a larf - you wuz dan ap there mate!' 
That line has entered into me and my mates vocabulary in general usage. Classic.
In fact, that particular phrase was asked about as part of the BBC World Service pages on Learning English.
BBC: "The line 'You was done up there mate' - what does it mean and where exactly does it come from? Probably not from America?!"
Karl: "Oh yeah, 'what a laugh - you was done up there mate!' It's like, you were... How can I say? Yeah, 'the wool pulled over your eyes', 'you were done badly by a deal there'. I live out in the east of London now and I'm fascinated by dialect and accent. I'm fascinated by English, you know, as spoken by other nations - and certainly as spoken by people in the east of London! It's fascinating, it's brilliant."
You can read both parts of the World Service pages called Singer and the Song here:
Part One and
Part Two. These deal specifically with Karl's lyrics and give you a chance to test yourself and knowledge of those words.