How to I work out how many shrubs I need to make a boundary hedge?

Is there a general ratio of shrubs per metre or anything like that? It's for complying with the landscaping condition in our planning permission and I'm loathe to fork out another couple of hundred for a landscape architect. It might seem a small amount to some people but it's a lot of money to us!

Not an expert but just going through process of ripping out garden and starting from scratch. Last time around, I planted too many too close and ended up in jungle territory. So this time I will (a) choose the type I want ( I like Kerria Japonica) (b) check in gardening book the eventual height and width and (c) plant accordingly. Might make some allowances for casualties.

mf

With standard hedges, the Garden Centre suggested a gap between each shrub of about 18 inches to 2 feet.

Magoo is right and also deciduous hedges generally grow faster, are cheaper to buy, and recover faster from damage than evergreens - that said all of mine are evergreens . Here are a few sites worth checking out.
[broken link removed]

http://www.derryleatrees.com/

Thanks lads for the replies. I managed to get an answer yesterday by ringing a garden centre. We have to match the existing boundary to comply with the county councils condition so whitethorn is what we have to use regardless of how much we might hate that and like something else. It's not a bad plant luckily but god they don't like to make things easy on you when your building!

Good luck gardening.