Topic

Having checked the fuse and unable to remove the horn plugs, could anyone tell if there is a common reason why my horns don't work on my 2000 MGF.

Bad earthing?

I’ve always considered the connectors used on the horns to be the easiest to remove on the car, some connectors seem to be “one shot” plug in & that’s it (try the wing mirror adjuster).
There is a bar across the connector below here the wires enter, depress that whilst pulling & with a wiggle it should come away. A pair of wires over from the battery to the pins on the horns will verify.
A few months ago there was a question on this subject & it turned out to be the clock spring in the steering wheel. This wasn’t a failure of the spring but an incorrect replacement & that happening twice is vanishingly small. When I had problems with my horn (that’s a wide open comment for Cobb’s) it was the red box behind the fuse board but I’d be looking for something more straight forward as the only one of these to fail, it seem, was mine.
And yes look initially for an grounding fault.
M

Is the car new to you and the horn has never worked or have you had the car for some while and the horn has only recently suddenly stopped working ?

If the latter then it's worth retracing your steps on any work that has been carried out elsewhere on the car recently. Disturbance caused by other work is a major cause of sudden electrical malfunctions and the first thing that needs to be eliminated.
It could just be that the horn itself has genuinely worn out so you need to get the connectors off and check there is voltage when the horn button is operated.

Check the wiring diagrams for your year of F on this site and see if there are any other fuses or relays in the horn circuit that should be checked. Several circuits on the car have more than one fuse. Has anything else stopped working at the same time ?