Don't include us in the numbers staying anywhere because they're all so near that we can come over in the car for the day - or meet up wherever adventures are being had nearby etc.
To the houses listed...
I know exactly where the bunk barn is, it's on the High Peak Trail and we had a picnic and walk there a few months ago. It's pretty isolated, but also popular and very nice. There may well be a decent bus route there because it's deep in hiking territory but I will have to check - I usually zip past in the car. It's very close to Arbor Low, Gib Hill barrow, Youlgreave, Chrome Hill (the Dragon's Back) and the Silent Woman pub in Earl Sterndale.
The one in Sherwood looks like they'd be flexible with numbers, it's not rented via a holiday agency and in my experience they're more flexible/open minded. Retford, bizarrely, is not an easy trip to Loughborough by train - you need to go into Sheffield and then out again to Loughborough. Though would you only need to do the Loughborough trip the once? Hmm - think about that one!
The one in Turnditch, Belper is 4 miles from Belper station, which is then only 43 mins to Loughborough on the train - an easy trip, you change at Derby. And a group in a taxi for a 4 mile journey would be cheap.
Anyway, I never told you about a dining opportunity none of you would want to miss in the Peak District:
Wurst!