I need some advice on the type of tube required for the repairs of my buggy please.

I currently have 35mm OD X 2.5mm and two other smaller size tubes as angle braces and steering mounts.

It seems to be the correct size as per CAMS but is there different sizes for different grades of steel.

I'm guessing it's mild steel but not real sure.

What is the cost difference between mild steel and Chrome Moly and what are the benefits.

The buggy is 95 build and has no cracking but the welds make me look good.

Any help or advice (besides don't hit another tree) would be appreciated.

My wife has definitely covered the tree comments.