Not a supplier but a manufacturer...
I recently purchased a Test-Um ValidatorNT 950 and it is a BRILLIANT piece of kit. I have had it two weeks and there has been 3 software upgrades in that time which have added lots of magical new features!
I have had difficulty installing the Plan-Um software on my iBook so I tried the 'LiveChat' on the support website, unfortunately the guy wasn't too helpful but did pass my problem on to someone else who replied the next day (time difference with Colorado permitting) and solved my problem to a satisfactory standard immediately!
These guys are great! I hope that EduGeek is going to be able to work with them in some way... more news soon.