We're unable to get to the vets until Monday and wondered whether any one knew whether
metacam was ok to give to a young collie x jack whos 10weeks old who has damaged her
foot under something that fell on her. shes limping a lot.

if its bad enough for you to consider given metacam. why not phone your vet, they will do out of hours....after all if your pup is in that much pain there may even be something broken? Best be sure I should have thought

Metacam is a POM and should never be given without a vets authority.  I would see the emergency vet myself as this young animals growing bones could be effected if a break was not attended to promptly with immobilisation if appropriate.

I would contact the emergency after hours vets.  Metacam is a powerful drug, and it shouldnt be used unless directed to do so by a vet. 

How is the pup doing? Have you spoken  with / seen a vet?

she needs to see a vet, if the vet prescribes metacam then you know it's OK to give her. Metacam is dosed depending on the bodywieght of the dog (amongst other things) and needs to be given under the vets supervision.
Aside form this, it's best that the exact cause for the limping is found via a vet examining her (eg, is it broken bones or bruising etc), rather than just treating the pain.