John, I think you hit the nail on the head there.
In a detachable lead, the fuse is there to Protect the lead and it is up to the equipment manufacturer to provide suitable protection for the equipment by means of the equipment fitted fuse and appropiate rating.
IMHO, its a time consuming affair to mark the leads or to try and police the use of leads on differen equipment.
By reducing the fuse rating in the lead you are provided an extra safe zone for your users to reduce further the risks of the age old problem of lead swapping.
Admittedly the policies are all decided at local level by means of trial and error, what works for one person may not work for another. Provided we can stand our ground on the choice we make then that should suffice.
John, we pretty much adopted the same policy at Haslar, by changing the fuse to a reduced level and marking the lead and equipment with seperate tested / due stickers so that if the lead was to become detached it would still have some identification of its suitability for use.
Rog Rocks - provided the cable and plug is manufactured to 1363/a then I cant see any problem of using long leads. The longest i have come across in general use has been the 3m type provided by RS, however there may be some 5m versions available. I wouldent choose to make up a long lead, but would choose a pre-fabricated off the shelf one as you will be guarenteed that it will pass earth continuity tests at the required levels.