FlyBoy,
I live just over the road from Chalgrove airfield. Normally the only movements there are either Martin-Baker's King-Air ot Meteor test aircraft. As far as I know (and I haven't got my Pooley's here to confirm it) you can only get permission to land there if you're doing business with Martin Baker. I'm afraid you'll only get a definitive answer by phoning them (01865 892724 according the on-line AIP).
I doubt that the strip at Lewknor is an option - its used by the London Parachute club, and I think is operated under the 28 day rule.
Brooklands