From Nick's main notice:

The forum will be unavailable on Monday morning, 3rd June for scheduled maintenance, while we upgrade to the latest version of vBulletin 4.

The downtime should be in the morning (UK time) only and we expect to have the forum back by lunchtime. Any 'unexpected extensions' to this will be posted on our Twitter and Facebook pages, but we expect the work to be uneventful, and have the forum back in time for me to enjoy the rest of the day in the garden with a cold beer!

Many thanks, Nick // Beechwoods