Stuart Webber 01884 860165/07740399138 is near Witheridge, he advertises in Mole Valley Farmers' Newsletter and our parish magazine. He is very good but is the other side of Crediton from Okehampton.
Regardless of the contractor, be very cautious regarding the wood which you use. If a contractor supplies the timber, then check about any warranty against rot. If you buy the timber in for yourself, and most contractors will encourage this, when the posts rot, and they will, then the contractor is absolved from all responsibility.
I'm now retired from running my own contracting business, and I have one particular Estate , where probably 60% of the 15000 metres of fencing, has rotted posts. Not funny, and all that I'm offered is the timber as a replacement, with timber in lieu to cover the labour costs.
Many posts with a 15 year warranty are rotting off after 3 years.
Be certain of your warranties, and get them in writing, including a responsibility for the labour costs, which will probably be in excess of the timber costs.
Another point to consider is that if timber has say, a 15 year warranty, and it rots off after 5 years, then the balance of the warranty is only two thirds, not all the 15 years, so they'll only replace two thirds of the timber claimed! After 10 years, then it's not worth pursuing.