The Post Office does pretty good travel insurance. Remember that travel insurance covers you not only for medical insurance, but for the whole travel bit (the Post Office insurance covers you from the minute you leave home to the minute to return home), plus you are covered if any of your things are lost or stolen. Buying travel insurance in advance also means that you are covered if there is a crisis and you can't go on holiday (eg husband/child/parent becoming ill, yourself becoming ill, your boss being incapacitated in some way and you having to stand in).
Anyway, there are loads of website to book airline tickets, skyscanner and opodo are two I've used, plus there are the airline websites themselves.
btw I think you'll enjoy it in the US as you already spell like them - if you're British you are travelling (with a double l)!