Might be better for me to buy the powdered form of B12 or I might lose the quality in transit over a couple of weeks?

You're right, the powdered form of B12 is less likely to lose its quality and potency in transit. But it's unlikely that any methylcobalamin you order online will significantly lose its quality and potency in transit, unless of course the vials or ampoules are opened by someone or exposed to extreme heat or light. So regardless of who you order from, I wouldn't worry too much about the loss of quality or potency in transit. It's really only once it's opened that it can start to go bad. So once you receive the methylcobalamin, open it and start using it, you'll want to store it in the fridge. Cover it up in the fridge and keep it away from any light. Wrap it in aluminum foil or put it in a brown bag.