Topic: key vascular plant abundance records

I wonder if someone could help.  I'm trying to get hold of abundance data for a number of key vasculars nationally if possible, or regionally over the last 20 years (1994-2014). 

I'd like to compare national trends with some local data I have the following species:
Early march orchid (Dactylorhiza incarnate spp. pulchella)
Purple butterwort (Pinguicula vulgaris)
Marsh helleborine (Epipactis palustris)
Pale heath violet (Viola lactea)
Yellow Bartsia (Parentuceillia viscosa)

I've tried the BSBI dataset download, but can't seem to find the abundances (if available). 

Any ideas where I might be able to source this data.