It was a State Visit- i.e. Head of State to Head of State, arranged over two years ago, long before the Iraq crisis and all that. Even the most important countries can't have one more than every 10 or fifteen years, or the Queen really would have clashes in her timetable. So Reagan was the last US president to get a State visit. Why Bush was next I know not. But he didn't get to address parliament- he was probably relieved!
The irritation over the helicopters really has its roots in the fact that Mr. Bush was the first state guest to refuse to arrive by driving down the Mall in an open carriage (or even a closed car) with the Queen, when that is the regular form of welcome extended to all state visitors on their arrival in London.