Yes, not a member of ACME but ridden most of the Essex events over the years. I organise the events over in Hertfordshire. You saw me at first control Knights Templar before I disappeared up the road.
I don’t know your heart rate zones but from your Strava would I be right in thinking most of your commutes are tempo?
I successfully completed PBP 15 when I had a 40km commute 5 days a week. That was pretty much tempo with some VO2 max up a 5 min hill. In addition I’d do an easier social 3 hour ride on Wed evening and do a longer easier ride on the Sat. Sunday was my one day off the bike. I completed my qualifying series and that was it. I don’t have that commute anymore and have to be a bit more structured with what I do. But if I still had that commute I’d likely still be doing it unstructured like I did back then.
The thing missing from your weeks are the longer easier rides. I don’t know if this is because you aren’t doing them, or simply not sharing on Strava. These are the only real difference between what I did in 2015 to success on PBP with what I see in your Strava.
The longer easier ride will over time see what currently appears to be tempo pace become to your Z2 pace. Over PBP distance you’ll mostly be at Z2 pace and thus want that as high as possible. I see a lot of riders who can hold tempo for upto about 300km, but beyond that their average speeds crash as they can’t hold it anymore nor their Z2 pace. Thus they seem fast on the shorter events, but it doesn’t scale at the longer durations beyond 14-16 hours elapsed. They start to go backwards after their initial surge.
Having said the above; it’s rarely fitness that catches out those who qualify and start PBP. It’s all the other things like drinking, eating, dealing with the heat (as a Brit), time wasted off bike in controls , sleep management, keeping your gps charged etc. not having clean water bottles. Not realising how cold it gets at night etc.
Back to training. I wouldn’t do anything extra during the week. There’s more than enough going on with the commute there. But see how you can incorporate some regular longer easier rides into your weekends.
I’d have a few chats with Tomsk and the ACME gang. There’s a lot of successful PBP knowledge local to you. You might have to buy some pints to extract all the info. Try not to overthink training you’re already in a pretty good place with your regular consistent commute.