Friday 18th December will be the date.
As for destination, personally, I'd really prefer not to go to Southend. Although it would have a halfway stop at J31 services, and I like arriving at Southend, seeing as almost all of the route is through built-up areas, it's most of the actual journey I find rather boring, apart from the last 5 miles!
Whitstable is probably the easiest route, but as I mentioned above, there wouldn't be a halfway stop, and it would be a question of hoping one of the cafés in the High Street opens around 8 am.
Although it's a longer distance, if we look at Bognor, then we can use Pease Pottage services near Crawley as a halfway stop, and on the assumption it will be a fairly small group of 10-15 max, then upon arrival, there's the station café in Bognor which I'm certain will be open, or Jasper can recce something else that opens early on a Saturday.
Although I like Whitstable very much, I'm inclined to look at Bognor simply because it doesn't feature much on the official rides list! Route-wise it would be the traditional Brighton route as far as Gatwick, then south through Crawley to the services, then a back road to Horsham linking up to the published Bognor route.
Anyone else got any preferences?