I have a conditional offer from Durham in International Commercial and Trade Law for International Commercial law from Southampton, for the same subject from Manchester and Glasgow...
I am confused as to which one should i pick of these...
will be really helpful if someone could clear these doubts

I really consider that Durham is better for Commercial Law than the rest of those unis you mentioned. Not only Durham's reputation but also the subjects they offer seem to me more completed and highly concentrated on commercial and trade law.
Besides i think durham is cheaper than the rest and also the living costs are less than the rest.

Good luck with your decision

Lets see what the rest have to say :)