Hi UK123, and welcome!
I also used to "work from home" two days a week where I would essentially drink from about noon until whenever I passed out. How much actual work I got done was negligible but it was a fantastic excuse to start drinking during the day and every weekday rather than waiting until 6 or 7PM. Like you describe, I would be somewhat productive for a few hours and then crash. Those hours got shorter and shorter for me.
I quit drinking completely a little while back because I couldn't manage my life anymore (nevermind my job) but I also started forcing myself to go into the office each and every day. I could not (and it is still likely too risky) take the risk of being at home. I am way less likely to drink or be tempted while around others. Made a world of difference...
Is this a possibility for you?
Welcome again and please keep posting!