I would like advice about the labor law, working as a picker in a warehouse, lift heavy things, soon I go to surgery for thyroid, I had 12 weeks support plan, but not my company don't want supporting me more, I have long been waiting for occupational health advisor, who will decide on What percentage I will work. My manager told me definitely decide on the occup. Advisor of the least 85percent, but people have problems work on performance in our warehouse, the manager threatened me even without witnesses from warehouse may cancel my contract even though I'm still not Occupational Health Advisor. Can my company do that? I have never had the absence, stage. Iwork slower but I'm trying, despite my health problems. I am afraid of if I come to work after surgery, to be released from work whatsoever on my health. I work full time . Thank you

Aside from what company policy is, and not discriminating based on that policy, there is no law that requires a company to keep you if you are not physically able to do the job. The exception would be if you had been hired as a disabled worker from the beginning.
Most warehouse picking jobs are very hard work with strict rules about breaks and even going to the bathroom, so don't you want to find a desk job, like perhaps a customer service rep?

Are you a member of a union?

First by the wording, I would say this is not the US. We need to know where it is for a proper answer

I live in the UK.

I am member www.unitetheunion.org