XC schooling venues are limited esp if you limiting yourself to the borders. The ones across the south/central of Scotland that I have been to are:
Holefield, Kelso - permanent XC fences usually on perimeter of field track with three height options. They also have a decent water.
Edderston, Peebles - XC fences over farmland, usually open all year (!!), course has been recently has some much needed TLC several height options at end fence but fences tend to be more old style XC/hunter trial fences than BE. Lots of little things up to approx 90/1m. Water splash. Great hill for fittening work
Craigbeck, Moffat - brilliant course but not sure since new owners if able to be hired anymore. Mainly BE90 - Nov with some smaller logs but not the place I would go to for a first outing.
Smeaton, East Linton - many XC fences built near the garden centre. Lots of logs and various other well built fences. No water though. I tend to go here with youngsters or for a school after the winter. Usually opens March/April depending on ground/weather
Greenfields, Drumclog - good selection of BE type fences with variety of heights up from small to BE100/Nov
Strathearn, Methven nr Perth - great training venue, great fences of all heights but one of the best venues for the bigger fences
Foresterseat, Glenfarg - great selection of all types of fences but course in only open at limited times per year
I am hoping that ISEC and RockRose will provide XC schooling in the future.
Edinburgh Equestrian Centre has stopped XC hires. I suspect due to the fact they has a lot of portables which the issues with securing the fences properly stopped them. There were a few fixed fences which I used to go down and play over but their website no longer gives your that option
Sometimes you can have schooling days round Hunt XC course after an event eg Duns and keep an eye out for PC events in dumfriesshire like places at Raehills
Ones that I haven't been to
Lindores, Fife - really wish to go there as looks really good!
Livery yard (who names escapes me) near Strathaven with some XC fences
Ecosse EquiX now called Avonside XC, north lanakshire
Also possible remembering Timpdendean may have some XC fences towards Jedburgh as been BE training there although only have been there a few years ago when area RC SJ was held there.