OK... I'll tell you what I'd expect as a bare minimum.
Four walls, a roof, a door that closes, and possibly even a window. Some kind of platform for sleeping on, rather than just the floor. Some kind of sturdy shelf for cooking on, and access to water, which doesn't have to be inside, but shouldn't be more than a few paces outside. Some kind of toilet. I'd pay £5 per night for all that, and maybe even £10 if the weather was truly lousy.
Showers, electric and gas for cooking push it to the 'luxury' end of the scale, and by the time bunks and mattresses are included, I'd start calling it a hostel, rather than a camping barn. I might go as high as £15 for all that.
One thing I really don't like are camping barns that don't cater for guys who just turn up on their own, or with a mate. I've seen more than enough barns that I'd be keen to use, but they just aren't available to me unless I pay for the entire building... up to £60 or even £100 per night. If it's going to be marketed as group accommodation, make that abundantly clear at the outset, so that someone like me can look elsewhere.
ditto Paddy's comments
for me bare minimum, fully closable door, a window (or two), platform for sleeping if poss, a table and chairs/benches, a wood burner/fireplace, accessible water very nearby.
for the above £5-10 a night max
optionals but nice to have, a toilet and a food prep area
The barn in question is up at Watendlath in the Borrowdale valley. I personally think it is in a stunning location and once upon a time wanted to live there myself!
As it was once long term volunteer accommodation it already has a shower and 2 toilets inside, but with it laying empty for so long the rest of it is having to go through a complete re-think. So getting this feedback is all helpful. one of the current considerations is the sleeping arrangements, with limited options, due to the sort of space im working with, so knowing that perhaps mattressess aren't necessarily expected is a good point to mull over!
The exciting part for me is that this is just a small part of the space i have to work with, granted the rest is going to need a lot more work, but i'm loving the challenge!
Just catching up with this thread; I think I can describe myself as an experienced barn booker for exclusive weekend groups
Priorities are: wood burner or fire (summer is for camping; barns are for winter & it's a social thing), location, water source, cooking space, ideally separate living and sleeping areas (as groups don't conform to my bedtime & getting-up time). I usually get this much from a bothy, for free, so personally think sleeping platforms and mattresses (the plastic covered hygenic variety) will appeal to those who don't own or want to carry a decent sleeping mat. Toilet facilities are desirable for a group, though not too fussed if there is a shower (only staying for a few days). Also not fussed about all things electrical, although hot water is a distinct luxury.
After that, ease of finding availability & booking - for the Lakes I use these - £8.50 pppn seems ok and you'd be able to see on the website how much occupancy they get at that price. Of the ones we've tried from this site, St John's in the Vale is the favourite.
Not if you drop in it isn't. Well at least not in the one at Buttermere. He always charged the full £6.50 when I last went there. Not used them for years as last few years it's been in the hills with a bivvy and tarp.