I would just phone up and register that field under your CPH number, then you can move sheep around within 5miles without a movement license providing they are registered to your holding.
Re the land, you would do better to run an electric fence down the middle then you could support more sheep as you could graze one side then put them on fresh and rest the other side, so you basically continually have fresh grass and better for finishing. You would need to do the maths to make sure the extra stock would cover the cost of the electric fencing, if you need to purchase.
If you are doing this for a good profit, go for a commercial breed such as a texel or texel cross to get the bigger carcass weight wise for market.
Sounds like you have a good deal there!!