In future you can also try http://www.thomsonfly.com/en/index.html for flights from Bristol. I checked your flights in this case and they came to £1287, so you're £27 better off with the flights you have. However, that might not always be the case.
Thanks Jay Jay, but I did look at Thomsonfly - for the dates I want and the numbers I require (4 adults, 3 kids), and I've got the figure as £1,761.83, all in.