If you are considering buying djembes for use in UK schools then watch out!!!
I visit hundreds of schools and see tons of djembes sitting in cupboards unused. The reason they are not used is because they are badly made poor quality djembes and frankly sound awful and are sometimes unplayable.. Often they are bought in bulk cheaply by a music service or provider who know little about the instrument. Teachers then experience djembes as an unpleasant thuddy sort of sound rather than the fantastic, diverse, energetic instrument it can be.
I have been asked to tune djembes which are frankly untunable. I saw some the other day that looked as  if they had cured hide heads rather than dry uncured goatskin! These were unplayable and untunable.

My recommendation if you want cheap but good quality djembes is get Bucaru Festival djembes which retail for as little as £35 each. They have fibreglass bodies and goatskin heads... or if you want proper good quality wood djembes go for Kambala unless you know a local professional african drummer. These start at around £75
If you are buying more than 10 you should be able to cut up to 50% off this price.

Reputable suppliers who will give trade and educational discounts:
Soar Valley music
www.soarvalleymusic.co.uk
Knockonwood
http://www.knockonwood.co.uk/

Buying cheap drums from an educational music supplier is very hit and miss and you are more likely to miss than hit. You could be spending your precious budget on ten completely useless drums whereas you could have bought 5 drums of very reasonable quality that would last you for years.