I think smallholders with livestock too big for the boot of the estate car really do need their own transport, a small P6e is not that expensive, can be towed by a normal family car and will mean you can get your livestock to auction and in emergency cases to the vet. It takes up to 8 sheep, quite a few goats and two 10months old pigs easily. Most smallholders will not need to transport much more at any given time. Any larger group (of sheep) I can organise a haulier through the local mart that will pick up from the farm for example
I doubt that you will have enough custom to make it worthwhile, you will need to pass a few exams on the way, get insurance cover. Speak to the likes of Gordon George of Ardross Animal Transport to get an idea if it's a likely goer.
I don't want to dampen your enthusiasm, but think you may just not get enough custom.