British humour: self-deprecation and irony
British humour is often understatement and self-deprecation. Saying the opposite of what you mean, with a flat face.
When it rains hard: 'Bit of a drizzle today.'
When something is terrible: 'It's not ideal, is it?'
When you are very upset: 'I'm a bit cross.'
The skill is reading the GAP between the words and reality. The bigger the gap, the more emphasis.