I started with cheapish shoes from JJB (30/40 quid), they have a good range OF beginners stuff. Middle of the road shoes are great for road running but get something decent if you go off road.
I run off road marathons and choose Salomon XA PRO Ultra GTX, just because i want them to last a little longer than 6 months. In the long term i believe they are worth the 90 quid, which i must add is a lot of money to me.
Montrail Highlander are great for shorter off road/fell, plenty of grip, a decent amount of padding and are available on the web for 40 quid.
Inov8 are worth staying well clear of. IMHO