It seems the 52 is the good fit for you. If you've been riding it and you like it, go for it.

Don't take the Rivendell guidelines to heart. Go with what you feel is comfortable. I also wouldn't put too much stock in the spreadsheet from the LHT/Google Group (although it is helpful, thanks for pointing it out) because if you notice, they have guys from 5'8" to 5'11" on a 54, a 5'10" guy on a 52, and a bunch of 5'10" guys on 56's. I think this shows that you should pick something you feel comfortable on.

I am going through something similar. I ran my dimensions through a couple of online fit calculators that suggested I go with a 52 or 54. I 5'9" with a 33" (84cm) PBH. I test rode a 56 Surly LHT because that's all the LBS had. I had to put the seat all the way down just to reach the ground and I felt stretched out across the top (although it had a longer stem). Overall, it was OK, but I just felt it was too big so I opted to order the 54, not wanting to go all the way down to my low range. It hasn't come it yet but it should be ready tomorrow. I'll let you know how that goes.

One good formula for fitting a road frame that I found was BIKE FRAME SIZE (in cm) = Inseam (cm) x .67. So if you put in your PBH of 80 cm... 80x.67=53.6 You are almost right in the middle of the two. There's also a good fit calculator here too.