SSwitch sold 700.000 units in 2017
so far, 1.3 million consoles have been sold in UK in 2020. it's likely Switch is close to 50% of marketshare, which would mean 650K withouth the last quarter. (in USA Switch had a little less than 60% marketshare, but UK is a worse market for Nintendo)
idk how much Switch sold in 2018 and 2019, but you can clearly see the growth from the first year