I'm trying to decide what bike to purchase. I'll be mainly riding off-road on birk tracks, woodland roads etc, some hills and downhill, plus a smalll amount on the road - I have around £500-£600 to spend (1000USD) - would apprecioate anyone's advise on Make/Model etc
That's a very open-ended question. The fact you are on BF tells me you already know to stay away from department store bikes. Most major brands will make a bike to suit you, and be of good quality. Start by going to some trailheads where you plan to ride, and ask riders if they like their bikes, or what they would change, and ask for their opinions. Most riders will be glad to answere questions and many will talk your ear off about their bikes. Find out which local shop is the best, and go from there. Best o'luck to ya!