Evenley Wood Garden is a delightful wooded garden full of snowdrops in February, and lilies later in the year. It is not an enormous garden, but it sometimes has events on at the week-ends such as a rare plant fair, or car rally so it is worth checking out their website.
There are cakes to enjoy when you visit, plus plants for sale so it is an enjoyable hour or two and you can always combine it with a visit to Buckingham or Brackley which are the two nearest towns.
I bought some snowdrops from the garden many years ago, and they still flower every year reminding me of my visit.