Ambroid Pro Weld is basically a solvent that is used to bond plastics together. Unlike 'normal' plastic glue found in most hobby shops, it can bond ABS, Styrene, Butyrate and Acrylic plastics.
Also, because it is a solvent rather than a very thin glue as such, it doesn't leave any ugly drips or blobs on the finished model.
It works by capillary action too; you hold the two parts to be joined firmly together, and dab a little of the stuff at the joint. It is drawn by capillary action into the joint and sets the two parts together. Like Poly Cement, it actually dissolves the two surfaces being joined to form a surprisingly strong bond.
It also sets faster than CA glue since it evaporates so quickly!
The stuff is rather nasty though (it is carcinogenic and teratogenic, since it is pretty much just Dichloromethane - the same stuff found in paint strippers like Nitromors). I suspect that it is for this reason that it probably doesn't sell much/fast in the UK and why stockists don't carry much (and therefore keep selling out).
I can just use actual DCM - and save myself some money too as it is much cheaper than Ambroid Pro Weld - but I find that the 'diluted' Pro Weld does the job just fine and hopefully also reduces my exposure to the stuff during any one session... I figure that's worth two or three quid!
Trouble is, the stuff usually costs around £3 a bottle, and everywhere online that has it in stock (not many places!) charge you ~£4 plus £3-4 on top for shipping. That makes a 60ml bottle cost around £8 or more!
So as you can see, any help in locating some would be greatly appreciated!