Thanks for the suggestions. I think it's right to stick at 5,500 yards because it asks a lot of the course to remain interesting throughout the round and Painswick certainly does....
Tommy, you need better weather for playing Painswick, but you'd get a very fair idea of the course just by walking it - and you'd know immediately that you simply have to play it in better weather - and join Sean at Kington, too. You would be entirely at home with the walkers and dogs - just like Royal North Devon. By the time of your visit a lot of courses will be in winter mode (that doesn't mean snow) but back tees get taken out of play, replacement holes are sometimes brought in to play, greens are kept woolly and so on. So you need to think of the best drained courses twixt Oxford and Devon. Broadway is reckoned to be the best drained course in the country. I haven't played it for years, but there are a number of good holes and the views are tremendous (Sean might well chip in). Near Oxford I'd go for Tadmarton Heath close to Banbury which has tons of character (though Sean was only so-so on its merits - he posted about it quite recently). I'm not as up as I ought to be on the downland courses of Wiltshire, but Ogbourne Downs, Marlborough, High Post are worth a shout, and maybe someone can speak of the merits of Tidworth garrison, Upavon, West Wilts and North Wilts.
Of course, if you've not already done them, you could detour south to take in Broadstone, Parkstone, Ferndown and Isle of Purbeck in roughly that order. They're good winter courses.
Back to the short courses, I used to play (back in the 70s) fairly often at Coombe Wood in Kingston, Surrey. It measures 5299 from the back tees, and it was certainly under 5000 from the yellow tees we played. Yet it felt no shorter than Highgate (which was the other course which welcomed our motley society) which measured 5964 from the whites. Coombe Wood doesn't have the character of Painswick, but I remember fondly quite a number of really good holes.