Hello,
If you haven't kept sheep before I would suggest you go for a docile easy lambing breed. I would also go for a breed that is known to taste nice and fetch a good price for the meat. Personally, I would recommend the breed I keep - Llanwenog Sheep - as they meet all those criteria. You can find out more about the breed at this link
http://www.llanwenog-sheep.co.uk/As far as fencing goes, you could invest in electric fencing. This is a lot cheaper than permanent fencing. It also means that you can move the fence boundaries so you can "rest" part of the land - which will keep your pasture and your sheep as healthy as possible.
Llanwenogs are less likely to escape than other breeds of sheep as they have a very calm nature. You will get good money for the meat so that should pay off the cost of the electric fencing quite quickly.
All sheep, apart from the primitives, are quite expensive this year as meat prices are so high (I am told that this is due to most of our UK lamb being sent to France). A non-primitive breed sheep will probably cost you at least £90. If you buy in the next month or so, you should be able to get ewes in-lamb.
If you decide to go for Llanwenogs, feel free to give me a shout and I will find out if any breeders close to you have any to sell.
Good luck with what ever approach you take!
Jane