For £150 you have a couple of options, either

- A very good stick arc welder
- A basic but still good mig welder

My arc welder set me back £30 from macro. Although it is cheap, nasty and tricky to get a good weld going.

I dont have much experience of mig welding so I cant advise you here.

An arc welder will happily weld all steels and will weld up your steel box section no bother. Arc welding is a little more tricky to get the hang of but it can lay down a nice weld when you have the nack.

Something like the following will allow you to weld up to 5mm steel sheet or box section.

http://www.diywelding.co.uk/product_...-4056854A9307}