Having lived abroad, I know there are many, many good things about living in the UK, but for me the worst are:
The expectation that we should all have great public services, and we moan when anything goes wrong, but in the last 10 years we have refused to vote in any party that will raise certain taxes to pay for said services in line with our expectations.
The education system and the amount of emphasis placed on exams. And the fact that it's usually the teachers' fault if there is any failing anywhere, rather than the fault of government policy, chronic underfunding or even indeed the parents.
North-South divide.
An overinflated sense of our own importance as a country, particularly nowadays.
How people in the service industry are treated.
The trains. They are absolutely shit in some areas: expensive; over-crowded and perpetually delayed. Kind of links in with my first point though.
Overpriced property and a tendency to view economic success largely through the prism of property prices. Also an obsession with "getting on the property ladder".
The mainstream media.
Increased intolerance of those who emigrate here - although I do recognise this is not an attitude which is necessarily unique to the UK.