My first attempt at solving this on the Comet was to spend £450 on a new Conways Honda clutch conversion. This runs in ATF and is set up perfectly. Unfortunately it didn't work.
The second attempt involved a 2p cable tie, and this has proved far more successful. Let me tell you more. I was chatting to an old guy a couple of months ago and he suggested a simple, but quite brilliant method of eliminating this. Just get a cable tie and fasten it loosely around the handlebar grip and when you leave the bike for any length of time, use it to hold the clutch in. Since I've done this with my crunchy Comet, the difference has been remarkable. Not only has the noisy first gear been solved, but the gear change as a whole is vastly improved to the extent that I now realise that I don't need a new gearbox.
Granted, over time it may weaken the clutch springs (we'll have too see), but I'd far rather replace them than start buying new cogs for a Burman gearbox.