Lots of Galium odoratum, at several locations
Carex pallescens at a couple of different places on the rides. This is a very occasional species, usually found on damp rides in ancient woodlands locally.
Ornithogalum umbellatum, on a ride edge. I have recorded this before from a different part of the wood. It is considered to be non-native in Northamptonshire, although in both cases at Southey Wood it was growing among semi-natural vegetation with no other apparent introductions.
Sanicula europaea, a local species of dry calcareous woodland, with one extensive patch growing near the car-park.
Aquilegia vulgaris, in the car-park, most likely an introduction but self-seeding and apparently well established.
Other species of note include lots of Astragalus glycyphyllos and locally frequent Oxalis acetosella on the more acid soils. Definitely a site to revisit later in the season!