Tripping over them yet again, I tried fitting a pair of Flexi wings (wheelarch liners). Being designed for an MGB they needed a bit of persuasion to fit a Magnette, but surprisingly, not much. They fit over and around the front suspension, for instance: usually there's a strut in the way. Easy to extend/adjust, and appearance is not an issue.
They're available from Moss, or Ebay etc for about £40 - £50 per pair. I know Magnettes don't usually go out in the rain, but sometimes it can't be avoided.....