I have a Camper Longflap and a Low-Saddle Longflap. I like them a lot. The only thing with them is that you need a decent amount of drop from the saddle to the rear tyre. I'm short and so had to get a Low-Saddle to fit on most of my bikes. I like them. Strong, waterproof and usefully sized. I used the Camper on a week-long tour where we stayed at motels/pubs/hotels. It held all I needed. I use the Low-Saddle on one of my commuters.

You also need to have saddle bag loops on your saddle. Brooks have them as standard, but if you have a modern style saddle you will also need to get the clamp on saddlebag loops. The Bagman support rack is useful for holding the bag of the back of your legs or up from the tyre. The Bagman is rated at 10kg which is a decent load.