Hi Nick (fellow Norfolk boy!!!) and welcome to the forum!!
I have an Autoplus 160, which I've had for around 20 years, it's never let me down I have to say. From what I've heard the later SIP machines aren't so good, but if you hang around, someone in the know will be able to help out.
I seem to recall the Autoplus machines are the better of the SIP ones, it's the smaller ones, MIGMATE etc which suffer wire feed problems.
What do you need to know about it? The data plate will tell you everything about it, min/max current, input requirements, duty cycle etc.
Controls on the front are simple, on/off switch, power setting (voltage) switches (min/med/max plus the high/low range one which gives you 6 in total), wire feed speed, that's it.