We never use less than a 7 amp fuse. The heavier duty cables we fuse at 10 amps. Equipment which is rated lower than that is protected by its own fuses. In theory there should be no problem with swapping leads (except on high current equipment where it takes out the 7 amp fuse - but better that than melt the cable) but the detatchable leads are a real pain because they generate so many "false" failures - just because they're not plugged into the equipment properly.
There was a notice put out by the MDA a few years ago which suggested that all detatchable mains leads should be tested every six months because they were prone to damage. Ours get tested every 12 months along with all the toasters and kettles. The company who do the work stick a laminated label round the cable with the tested date on - but not a re-test date - just in case they're late getting round to it next year !
They find quite a few with the insulation pulled back or a connection broken - sometimes the earth - so it's definitely worth doing.