Hi Everybody, thanks for the comments and any suggestions are gratefully received. There are a number of limitations with the very simple technical approach I'm using (like that 'alphabetic' week) but I'm looking to refine it.

There's now a FAQ on the map web pages including quite a detailed description of how it works.

My main aim is for this to be as crowd-sourced and self-sustaining as possible. That brings its own problems but I don't feel they can be solved by not being crowd-sourced, if you see what I mean.

Thanks to Mr Red for letting me know about this thread, I haven't paid attention to Mudcat for a while :o)

Thanks also for the mention of Jim Lawton's map. I can see very well how that happened and the only hope I have is that things have moved on so we are all much more web-aware and Facebook in particular has smoothed the communication problem. It's an experiment I guess.
I missed a trick not setting up a Facebook page before everything else but nevertheless the page is approaching 100 followers already and if that community can be encouraged from time to time to check their own entries and police a few more it might work.
It was Facebook that pushed the map from my original few entries to over 300 in 3 days (tapering off now). I was gobsmacked.
And Hooray, I've incorporated a manual reformat in my refresh procedure and dates are now UK standard.