What is the best way to get from Glasgow to Calais?

I am planning a trip to France this year to a campsite just outside Calais. I am travelling alone and meeting a friend over there but I am not sure of the best way to get there. I am not taking my car as I am not confident enough to drive in France, especially as they drive on the right and my car is for UK roads. I checked out the Euro Tunnel website but the only option I can see is for taking a car. Surely you can travel in the Channel Tunnel without a car? I'd be grateful for any advice, website links, costs etc. Thanks :)