Tree spacing for wind break?

I'm not sure about Whitebeam but we have hawthorn hedges as a windbreak and they're very good. We bought them as striplings which meant they got going faster than larger ones would. The farmers here tend to plant them in staggered rows (like a zig-zag) and space them about two - three foot apart to get a nice thick hedge. Once planted they have their tips cut off to promote side-shoots. If they get a bit thin at the base they get layered which shortens the height but makes them more capable of cutting down the wind strength. As for how far from the fence should you plant them, see what room you have and if you can get behind to trim them as I don't know if horses would eat them but cows do.

Whitebeam were very popular back in the 80s with the local authority here and there are loads of mature trees here. So what I say is based on my observations (from sitting in the shade of one while the kids play at the park).
 
I would say 2m is too close together. Their canopy is too wide for them not to be elbowing each other for space. There is a hawthorn within 2 m of a Whitebeam and it does fit under the canopy, but not happily. If you did plant Whitebeams you'd also be totally shaded out, RHS says they can get up to 12m tall 8m spread. The local trees are about 5-6m wide and maybe 8m tall maturing in 20-50 years. Time frame, will you be worried about this in 30 years?

I would say go for a hawthorn hedge (they planted one of them 10 years ago). They grow fast, are hardy are spiky-protection, loved by birds and are a great windbreak. I'd also stick a plum, crab apple or apple tree every so often. It'd increase species diversity, give you fruit and you'd be thinning the canopy out to keep them healthy and productive so it wouldn't decrease your light as much as a whitebeam with it's dense canopy would.

Modify, they planted 2 foot saplings closer than that and it was a hedge within 3/4 years.

Do you want me to take measure between trees and send you a photo of what they look like in a row? It's sunny today and I'll be to the park later so it's no problem.

Hello try Alder trees they like it a bit damper  and a couple of poplar if you have room  a London plane they take in pollution and shed their bark in early spring and you can claim they are environmentally  friendly have you tried for a tree planting grant that keeps cost down  jezza