Dorchester Collection's Coworth Park will soft open this September. Could be interesting as Dorchester have no experience of running a country house hotel!
Re: Whatley Manor, be careful which room/suite you go for. Of the rooms, #10 is by far the best. Of the suites, #24 is best - it's in the eaves, but it has the best bathroom in the whole hotel. Decor has improved here since they completely re-modelled the fine dining room (for the 2nd time). Lounges are very elegant and comfortable, too. Le Mazot, the hotel's Swiss bistro is eclectic and very Swiss, but then so are the owners. The Restaurant's cuisine, by Martin Burge, is justifiably 2-star Michelin, with loads of little amuses interspersed between courses. Best start off in the Lounge with a glass of something, at which point canapés should arrive.... It's worth staying here as the service is very good for the UK and the experience is wholly relaxing. Stylish spa, too.
Whatley is a more 'polished' experience than Barnsley House, but it really depends upon what you are looking for.