I've also looked into this and it seems expensive. If you aren't planning to buy it at the end then from what I've seen PCH (private lease) is a lot cheaper.
I haven't got one yet but from what I've seen, on
PCP you should expect to pay £350+ on a 48 month contract, however it will depend on your deposit obviously.
On PCH there are good deals on at the moment, seen deals closer to £250/mo.
From what I've read, you can get up to around 40mpg during steady motorway driving, but you should be prepared to get more like 30 or even
lower if you're really going at it.