See figure 1.3a - https://www.gov.uk/government/publications/migration-advisor...
Note that to the best of my knowledge, these numbers don't include the Afghan resettlement scheme which would further lower the proportion of employment driven visas.
Who indeed will pick the cotton.
I do not distinguish the far-left from far-right as they equally polarizing and extreme, and only seeks to pull people in the center towards them through violence, censorship and intimidation.
People in the center seeks a balance between the extremes. Some industries require immigration of labor force but it can't come with delusional ideologies that seek to manipulate the wages.