AIBU Deductions from pay in Probation Period

[IAmADancer]

I may be being unreasonable and this may be allowed but I started working for well known clothing brand in October. I’m on an 8 hour a week contract but am doing at least an extra 8-12 hours over time every week and have been given a key holder role (which is not something I applied for but am happy to do). I have also stepped in on quite a few occasions to help cover shifts when people have called in sick.
I received my payslip today and have seen they have deducted nearly £100 due to my being off sick. I had a sickness bug and couldn’t come in. I have also not been paid any of the OT I have done since I started in October.
My AIBU is are companies allowed to deduct money from your standard pay if you are absent through to illness?

Wow, there are a lot of misinformed people on this thread. Most employees are entitled to sick pay (SSP, that is) if they have been sick for 4 or more days in row, provided they earn at least £118/week. OP doesn't earn enough to qualify but many people do.

OP, you should still be paid for all the hours you have worked. See
www.citizensadvice.org.uk/work/rights-at-work/pay/problems-getting-paid/
I advise you to email payroll/HR giving details of the hours you've worked and asking them to pay the money that is owed. It needs to be an email (or letter) so there is a record.

Sick pay is very rarely paid in retail and never paid in probation. Even if you worked overtime during that month that would have compensated for your sick days, they have to keep them separate for HR reasons, I.e to track patterns of absences.