Buckinghamshire, The Long Garden at Cliveden with its topiary and statuary is really impressive. There is a Japanese water garden, splendid rose garden, woodland and riverside walks with magnificent vistas. House open certain times
https://www.nationaltrust.org.uk/cliveden/
See Full Details and Opening Times
Northamptonshire, Beautiful formal and wild gardens surround this wonderful Queen Anne House in Northamptonshire
Cottesbrooke Hall and Gardens
Northamptonshire, Kelmarsh Hall has a wonderful sloping walled garden with beautiful all the year round planting. See the colourful double herbaceous borders and the old fashioned Rose garden. Hall is also open.
Kelmarsh Hall and Garden