Fitting new horns
The factory-fitted horns are in a pretty awkward place. Sat just behind the front grill, under the cross-member, you need to remove the front bumper and grill to access them.
Partly because of this placement they are right in line for all the weather the car drives through, and like ours can seize up. We knew the wiring was fine, so it was just a matter of swapping out the horns, but didn't fancy removing the front of the car to do it. A quick look on the MGOC forums confirmed this was the sensible way forward. Luckily there are two steel plates either side of the radiator with made-to-measure space in front within reach of the horn wiring. You could be forgiven for thinking that this is where the horns should have been all along.
One of the plates has a ideally-sized hole already, so it's just a matter of a minute's work to zip a hole through the other one to match. (In case you're thinking, "I'll just take the plates off and that'll give me full access to the old horns", forget it as they're welded to the chassis and radiator - yes I tried.)
So horns in place and the MG now feels more complete. Beep!