I am no expert on contract law but that sounds unacceptable especially as cancer patients are covered under the Equality Act 2010
My husbands previous employers were both very supportive, he was off for 18months before deciding to take voluntary redundancy but positive from the employer side. We took advice about handling any potential issues from an employment solicitor as he was likely to be off for a long while........free session for half hour... that was also useful but we didn’t need it. if I were you I would speak with ACAS, if you belong to a union speak to them or get some advice form someone outside the organisation such as Citizens Advice or Macmillan Support
I hope it all works out for you and your health improves.
