Hi
I'm the technician at a technical college and we wish to buy a tig welding plant to use on ali.
Could enyone recommend a unit for around £500?
240v 0r 3phase
True enough a £500 budget is a bit low for an AC/DC TIG.
The real advantage you'll have is being able to use 3 phase. Single phase AC/DC machines sell for a fortune secondhand on eBay, but a lot of really nice 3 phase machines sell for next to nothing as so few people have access to 3 phase. That's the route I would take assuming you are allowed to buy secondhand.
For new at £500 you'll be limited to the Chinese eBay machines. No support and don't always last for very long. Also for a college you might have problems using a machine that might not necessarily meet UK standards.
As Omniata suggeted, £1000 budget is really the starting point for AC/DC machines sold with any UK support.
I hope I'm not too late, but I bought a TIG unit from R-Tech last summer for my school workshop, and I couldn't praise them or their machine highly enough. Yes, their kit have a Chinese chassis, but the bits that count are pretty much all german (siemens was one name that they mentioned). The machines aren't just re-badged crap either, they design the machines to their own specifications at their R+D facility in Gloucester.
Give them a bell and ask for Dylan Emery, he did me a really good deal. Their 160amp AC/DC tig is £695, which is above your budget, but it's well worth you giving him a bell.