Flying from Toronto to Boston you will have a choice of AA, UA or AC. None of the services will be on a proper / mainline jet -- they're all RJs AFAIK. Prices run from $200 to $250.

Flying from Buffalo to Boston is cheaper. Your nonstop choices are B6 (JetBlue), which can price starting at < $100, or US.

It is easy and inexpensive to take a coach from Toronto to the Buffalo airport. Far simpler and cheaper than hiring a car. The trip takes two or three hours including border crossing time:

http://www.megabus.com/us/schedules/...newdate=041208

As a UK national crossing into the States from Canada you need all the same paper you'd need if you were landing here on a BA flight from London.