Ok so I've just gone with it and done PUDPDCD for the first time...someone pass me the wine?!
Did the first part and on the 20th minute she finally went down just as I was about to do the walking out of the room while she cries bit. She went fucking ape shit beforehand, that was tough. She was bright red and so angry. At first I was tempted to ditch it and cuddle her to sleep but in my head I'm saying 'it's for the greater good...everyone will sleep. I can do this!'. And while I know it isn't a power struggle, I kept reminding myself that I'm in control. Everytime, I put her down as soon as she stopped crying, not when she was dropping off which is what I usually do.
Anyway, I've just come back downstairs with the monitor on and she started crying again so I quickly turned it down to try and keep myself calm and started timing...then...she went quiet!!! This NEVER happens - once she starts she doesn't stop. It didn't even last 30 seconds and she's back off to sleep! I have just crept back upstairs though to check if she's ok 
I think the first day of doing this must be the hardest bit as it's so alien to the LO, but I really want to persevere now I've started. I'm so determined. I've bought some earplugs for myself and DP and I'll be putting them in next time she has a nap and I have to do the same again.
As DD's room isn't ready yet, DP and I will be sleeping in another room tonight with some earplugs for DP, and I'm going to keep on with this, going in then leaving the room as the method suggests. I'm going to have my flask of coffee and Lucozade to hand as I know when I'm tired with little patience it's very likely I'll give up.
Will keep you all posted. Hope everyone has had good nap days