There will probably a tolerance that's acceptable. Not sure if that would be inside it - worth asking BMW UK customer care before hearing what the dealer says.
It's not pissing through it, but clearly it's not normal either. I think the question would be has it done it from new (are you first owner and is that 2800 miles all it's done) or is it increasing? If it's increasing, its definitely a growing problem and not just a characteristic of your particular engine.