Well, that didn't take long.
I've frequently looked at Gumtree ads offering a swap and thought "Who on earth would prefer to swap bikes rather than getting cash in hand?", so of course today I went out on the Firebird and came home on this.
It's a 2002 GPZ 500 S with just 4500 miles on the clock, plus a fair bit of sad neglect injuries to be healed. But mechanically, it's sound as a pound and goes like A SENSIBLE COMMUTER BIKE (or if my wife isn't reading, it pulls like a flipping train).
That was a straight swap, no cash either way, and it didn't even cost me a penny to swap bikes on my insurance. Plus the world has two more happy people in it, which has some inherent merit of its own.
Farewell, faithful Firebird, now go and put that daft grin on the face of your new owner.