I suspect I can only get 3 out of the above 4 criteria, so they're pretty much in my priority order. In between Oxford and London, I'm looking to spend 2 nights this July at a country house hotel where I can lounge outside in a garden reading or strolling if the weather is nice or inside by a fire if not. A spa for massages would be a bonus.
I've looked at Manoir aux Quat' Saisons but the only rooms available on my dates are 900 pounds per night!! Lords of the Manor looks very promising, but is sold out. Barnsley House also looks good, but they're not taking arrivals on the date I need. Gidleigh Park is a bit too far off my route, I think, as are most of the other recommendations in previous threads. (Both the Lake District and Cornwall are off the table, I think, although if I could get a quick train to the Lake District from Oxford, I might be persuaded...)
So, any other suggestions? (Thanks in advance!)