I was out in the back garden this morning, measuring and roughly marking plots. John Seymour (the late great) recommends deep beds 5' wide and up to 20' long, and I can only fit three in side by side at that width, so I may have to go with a three-year crop rotation, which isn't as good as a four- or five-year, but will have to do. John Harrison in 'The Complete Vegetable Grower' recommends, if you use a three-year plan, solanaceae (spuds and toms*) followed by brassicas (cabbages and relatives) followed by everything else.
*and chillies, capsicums, aubergines, tobacco, and deadly nightshade. I may one day try chillies and capsicums, but not aubergines, which I'm not wild about, and definitely not the other two.