Since moving to our place approx. 6 years ago we have planted some hedge rows every year and have learned from our experiences. As follows
After much observation of other hedges we have settled on staggered double rows with the plants 0.5m apart, giving 4 plants per metre. Rows also 0.5 m apart. Economical and effective.
Budget for canes and rabbit guards to protect from rabbits and hares. We buy the black spiral guards and cut them in half to save money and have found that to be adequate--though we don't have any rabbits, just the odd hare. We buy long canes and saw them up to to save money-----we are in Yorkshire !
I would say plant a minimum of 700mm from your boundary, and when fencing in front again allow a miniumu of 700, depending on what fence and stock you have in your field. We had a bad experience where we fenced a bit too close and the sheep could reach through and pulled them out !
When planting do not mix the spiecies as the stronger ones will smother the weaker ones, plant say 10 hawthorn, 8 variety a, 8 variety b, 10 hawthorn , 7 variety c, 7 variety d, and so on. Its not rocket science just divide the numbers up according to what you've bought. Plant a minimum of 5 of a variety at a time. (except holly where you can just stick the odd one here and there.
Plenty of web sites will give of percentages of each variety to buy,
We use Thorpe Trees near York after using them trying some one slightly cheaper then going back as their quality is spot on.
2 years ago we were buying less so bought the 2 year old plants (I think branded as 60cm to 80cm rather than 40cm to 60cm) and have found the plants to establish and flourish much quicker, if you can afford the extra expence you will have a hedge probably 3 years earlier (based on our experience)
Also keeping the grass down during the first couple of years by regular spraying with round up helps enormously, the rabbit guards make this job easier as well.
For fast effective planting, use a large crow bar (ie a big long straight steel bar) to dibble holes, have a 12ft fence rail (or similar) marked at 500mm graduations, go along row 1 making holes, then 2nd row can be done by sight dibbling in between to get your offset rows. Go along dropping the plants in. Get a wheel barrow of nice dry pourable soil from your green house or poly tunnel, use a trowel to fill the holes with this soil, wiggle the plant a bit to settle it then go along with watering can or hose pipe and water each hole.....job done !,
November /December is the best time to plant (plenty of wet season left for the roots to establish in case of a dry spring) . We usually have ours delivered so we can plant them through the xmas break. We planted 300 plants last xmas eve !
Weve done about 100m every year for the past 5 seasons---its been a learning curve !
Hope this is of help
stu