We managed to get in fairly easy, as we sold our house in Edinburgh, but still had to buy a building plot with land. It took us two years to build the house, and by that time our children were in school/nursery, so I had a bit more time to actually get going. WE started from a bare field three years ago, and only now are getting somewhere near to where we want to be. Our mortgage is not that small either...
We have found it quite hard to find smaller holdings (with houses) for sale in the Borders, as we are still in the Edinburgh commuter belt (my OH goes up four days a week too) and horse owners are also very keen on these size holdings....
I would certainly recommend to rent a field to run some sheep on to start off, or you might find a cottage for rent with a field next door, which would allow you to develop a garden, get some hens and sheep. I know people who have a floating farm code, as they keep all their sheep on rented land. You could also look into byuing some land that is sold off/split from a large farm, and then try and build your house on the basis that you need to be on the land 24/7. I have seen that done too, but it would need a full economic justification for the planning permission (the farm has to be viable as main income...).
Hope this doesn't sound too disheartening, Anke.
PS: WE are just down the road from Newtown, near Longnewton.