While I was tarting up the bike and eradicating the winter crud, I was looking at the shocks.
Humph, I thought, those shocks let the bike down a bit. The tops were rusty and need of repainting. After a minute of head scratching while I polished off the coffee and Hobnob that Mrs Thebike provided, I had the idea of compressing the springs with large tie wraps.
It worked brilliantly. After a quick spray they look like new again.