Thanks for all the suggestions guys.
I got myself a secondhand BOC Telmig 110A. It's one of the big ones, two man lift into my van. Works beautifully :) I only need to do up to 4mm, mainly body panels on my old Volksies.
Mentioned to a friend that I was going to buy a Butters 180 and he said he had an old BOC jobbie taking up floor space (one transformer is dated 82). £50, around half of a 'huge' wheel of 0.8mm wire, loads of spare tips, argon regulator etc.
Chuffed to bits & saved myself around £300.
What's the best way of attaching a chain to my SIP to turn it into an anchor? ;-)