It seems to me the second division of pub ownership groups have less than 500 pubs,probably due to 2016 legislation for groups larger than this.Thanks for contributions from Dave M and Aqualung.
Trust Inns -- 500
Fullers -- 380
Shepherd Neame -- 350
Robinsons --280
Thwaites -- 275
Brains -- 270
Youngs -- 270
Wadworth --240
Charles Wells -- 200
Sam Smiths -- 200
Again apologies if I have missed some obvious names.