During the 18th and 19th centuries, coppice woodlands underwent an 'improvement' period, which involved either (1) selective removal of more undesirable species with artificial planting / propagation of more desirable species, and (2) conversion to high forest (perhaps even the former followed later by the latter).
In reference to point (1), whilst many coppice woodlands only saw such improvement come in the form of gap-filling with Fraxinus excelsior and other desirable species, composition of other woods dramatically changed. For example, in the South-east Lowlands, certain coppice woodlands saw the introduction of Castanea sativa, Fraxinus excelsior, Corylus avellana, and Alnus glutinosa, whilst simultaneously seeing the removal of Acer campestre and, in somewhat of a paradox, Fraxinus excelsior, where the overriding objective of coppice was to harvest Corylus avellana poles. In the Western Uplands, Quercus petraea, and to a lesser extent Quercus robur, were selectively planted with the intention of subsequent harvesting for the leather tanning process and for charcoal to be sold into the metal industry, whilst Corylus avellana was selectively removed.
In reference to point (2), the conversion of coppice to high forest was driven by local demands (or even general neglect). Where action was deliberate, Quercus spp. were principally planted, though Fagus sylvatica was also planted in abundance (notably in the Chilterns and the Cotswolds) as, after a period of undesirability (due to its poor coppicing ability), it could now flourish within the high forest, continuous cover-esque style management regimes. Ultimately however, Quercus spp. planting was more evenly-spread than Fagus sylvatica planting.
Source: Peterken, G. (2015) Woodland History in the British Isles – An Interaction of Environmental and Cultural Forces. In Kirby, K. & Watkins, C. (eds.) Europe's Changing Woods and Forests: From Wildwood to Managed Landscapes. UK: CABI.