Thing #1: Fuses (unlike MCBs) are intended to blow at 2x the rated current, in continuous use. That's unless they are special classes of fuse, which doesn't apply to a hedge trimmer! So a correctly made 13A fuse should blow after a defined time spent passing 26A (too early - can't remember the exact spec: Google it!).
Start-up surges usually don't affect plugtop fuses (unless the conditions are really marginal), because of the conservative use of numbers, but they DO affect miniature circuit breakers (MCBs), because those are supposed to switch off at the current shown on the casing.
Thing #2: The two purposes of a fuse in the plug top (officially) are (1.) to protect against fire in the cable, and (2.) to protect people against death by electricity. Protection of whatever-it-is against repairable damage would be down to a separate fuse inside the equipment. This means a lot of domestic kit is fused so that the appliance is significantly damaged before the fuse operates. This is normal.
Thing #3: There is an expectation by manufacturers that anything used out of doors will be in a circuit with a RCD (residual current device). This could be at the consumer unit (mandatory for 17th Ed. Regs-compliant installations), or the plug-in type.
The RCD is very important in these circumstances: much domestic kit is "double insulated", which is arguably the most evil marketing term ever (after "tobacco is good for you"). All it really means is this: as manufactured, a double-insulated appliance has no earth in its cable, nor its case (if it is a wall-wart type of power supply), even if the earth pin of the plug is metal. So, if you damage the power cord of a hedge trimmer, it is quite possible that it will stop working, but with live blades (because the cable is caught), and they will stay live, as will the damaged cable, until long after you have grabbed that end to try to free it.
Of course it is likely that the machine will cut both wires, but if it only exposes the live one, the thing will also shock any bystander who tries to prise your fingers off - two casualties for the price of one! In these circumstances, an RCD may not trip initially, but it should switch off almost immediately a live-to-earth circuit is made, either through you or the hedge or the live blade touching the ground, and hopefully will do that fast enough to prevent sufficient joules of energy through the heart muscle to kill it (and the rest of you).
Double insulated supposedly means that any exposed metal in the appliance is doubly-insulated from mains (whatever that means). And yes, people do occasionally die when they go to untangle cables from hedge trimmers, mowers, etc. without unplugging the device. There are fewer incidents nowadays, because of RCDs.
. . .
So, your hedge trimmer should be fine with a 3A or 5A fuse, and you now know why 13A fuses are often supplied (it doesn't make the thing any less safe, and manufacturers only need stock one sort of fuse). That said, I usually check new kit, and nowadays it often does come with a sensible sized fuse fitted. I'd try 3A to see, but if you use it for hours at a time, consider 5A: The smaller fuse should mean a slightly smaller notch of evaporated metal when you cut through the cable!
