They can dismiss you for any reason in the first 2 years. You won't stand a chance of proving it was because of your diabetes.
Also, you would need to set out the outcome you want from conciliation or a tribunal hearing. You want the job back? Unlikely that would work well, imagine working in those circumstances... so compensation?
It is tiny amounts. Your legal fees would be more than you win back. The maximum they award is around £12k for something like basic sex or maternity discrimination.
Those stories you read of people getting 100s of k are because those people were able to prove high damages - their future career and earnings impact based on the ruining of their reputation or massive setback. They are usually bankers or lawyers.
If your job was admin then I'm afraid to say it isn't worth it. I recommend moving on.
However there is nothing stopping you from going to acas first. Sometimes it scares them into giving a small settlement for signing an NDA. Likely no more than a couple of thousand, or maybe a weeks notice.
Your other option is to force a good reference out of them with acas if that's what you're concerned about, not being able to get the next job because of their unreasonable actions. Might be an option.