Hi Kubis. Welcome to SR.
I identify with pretty much everything you have written in your post. I'm a similar age, also in the UK. I was drinking for a similar time, similar levels. Always starting late afternoon and then finding ways to drink alone. I was so powerful when drinking alone in my living room and always made my best plans to not drink tomorrow in my living room. I had amazing plans until mid afternoon most afternoons until I ended up back in the cycle.
Now add in trouble at work, a broken relationship and a realisation I have virtually no friends left all in the space of a weeks bender when the drinking cycles joined up, you have described me on Sunday morning last.
It's tough but you can do this. I'm five days in, starting to feel better already. Ready to start fighting the fight.
Lots of support and advice on here.