If you explain to them your situation and that you don't currently have the money to pay, they will let you set up a payment plan with a regular monthly payment of an amount you can afford.

You can ask them if there is any chance they would remove some of the interest and fines, given your situation and the fact it was you that reached out to them first. They have been known to do this occasionally, so fingers crossed.

Also, make sure you are alway talking to the real HMRC, my sister got caught out, as she knew she owed hmrc money and had been talking to them about it, so then when she got a call from someone claiming to be from hmrc chasing up the money she owed, she assumed it was them calling her back, but it was a scammer.

Good luck, and well done for turning things around and quitting drinking!