For Glentress/Inner i always stay at tweedside caravan park really friendly and although it looks drab on the estate its as quiet a place ul find honestly as for the showers must of fixed them there ace.
For mabie i stay at a campsite in beeswing on the main road (again quiet) you can cycle up to the trail at top near the darkside and ride down to the xc trail no probs.
For delbeatie i did try Kippford buty yeah expensive however you can join the trail just up the road in forest, but i now go to the otherside of the estuary and camp at Barlochan caravan park its great and pub in palnackie 5mins walk
As for kirroughtree i always treat myself and stay in the youth hostel in minnigaff its nice there is asite though in the village
hope this helps ul love the trails there they are amazing to ride. One reccomendation is when you get to the end of the red at glentress ul cross a bridge finish it off on the blue route there are some great jumps in there…