At the risk of bring some semblance of a clue to the debate; chalk grassland and heathland (as well as hay meadow vegetation) would have been present in the UK prior to the actions of man through farming.
The BBC Nature website appears to disagree :
“Chalk grasslands support an incredibly rich and diverse flora. Originally created when the woodlands were cleared, this grassland now relies on grazing and cutting to maintain biodiversity. The thin, lime-rich soils of this grassland habitat are derived from the underlying chalk or limestone rocks, and attract plants that don’t grow in other soils. Home to many beautiful orchids and wildflowers, and the insects they attract including rare blue butterflies, chalk grasslands have been in decline in the UK for the last 50 years. The best examples are found in Wiltshire, Dorset and the South Downs.”
http://www.bbc.co.uk/nature/habitats/Calcareous_grassland
Which suggests a diversity of opinion on the matter.