The experts on this site have no connection with HMRC so we are unable to make representations to them on your behalf. So, if this answer doesn't give you what you need, I'd prefer if you didn't rate it as a poor or bad answer and just leave it. There is no obligation on you to accept my answer but I don't want an answer which will be technically correct unfairly rated.
Assuming you were not in the self-assessment system which required you to complete tax returns when you worked in the UK which I very much doubt, I'm afraid that you are out of date to make a claim for repayment of tax deducted through PAYE for the tax years you worked in the UK. Take a look here
for the time limits.
You are out of time but if you don't do something, you know that htere will be no repayment to you. Nothing ventured, nothing gained. So, the only thing I can suggest you do is that you make a written claim for overpayment relief following the procedure here
and explain what happened in your case, ie you lost the first repayment payable order and health issues prevented you from dealing with your UK tax situation, and appeal to the better nature of HMRC. You can send your claim to the address at the bottom of the page here
I hope this helps but let me know if you have any further questions.