Might be worth checking your doors hinges too - you can get a 'repair kit' for each hinge, containing new bolt and the 'olive' that wears out (even quicker with a heavy modular wheel on it). The kits cost about 70-80pence per hinge plus VAT from Craddocks - so for about £3 you can replace all three and it makes a real difference to the back door.
The swin-away carrier probably is the way to go, but changing hinges might mkae life easier while you have a look around.
