but humans are not like other animals or life-forms; many if not most humans today do not grow or find their own food, and only that tiny proportion, relatively speaking, that are food growers need to be on good growing land. Food is preserved and stored and shipped globally, it doesn't need to be grown where people live. People might need to move to escape excessive heat however.And so now, metaphorically, humans will follow the flora, fauna, and the rest to higher elevations and higher latitudes in order to find the conditions in which farming specifically can thrive. We have the advantage of easier travel from one area to another than most other organisms, but we'll still need to compete with those already in the new areas (current residents, land devoted to factories, best access to transportation and waterways) in order to keep growing the same crops.
It will take some intensive planning and maybe zoning to ensure that land can be available for agricultural development in currently non-agricultural areas in your north and west, while still preserving the rights of current residents and businesses to continue.
Climate migration at a micro level, here we are.
Fwiw, areas in the north and west of England and Wales that are not cultivated or are just pastoral are usually so because they are quite unsuitable for arable or horticultural use (e.g. the Lake district, Snowdonia). And the UK is not like the US with vast tracts of empty land just waiting for someone to take it in hand.