So the P38 likes to use coolant, and i think most of it is actually just leaking out than anything nefarious.

I've fixed a few engine bay leaks, but while working on it changing the plugs the other day, i notice a puddle of coolant on top of the LPG vaporiser... Theres no way coolant could have dripped onto there, it must've come from the vaporiser itself?!

Looking at the vaporiser, it appears to be in three pieces. i guess a coolant loop in the centre, then the two actual gas parts on either side. It seems to be leaking from the seam between them. It also has that sort of red crystally look you get when coolant has been leaking and evaporating away over time...

Anyone heard of this before? fixable? Or new vaporiser time?

It looks very similar to the Bigas RI-21 vaporiser that tinley tech sells.

Heard of it lots of times. Vaporisers can leak just like anything else when it starts to get a bit long in the tooth. If it's a Bigas, Tinley Tech will also sell you an overhaul kit with new diaphragms and gaskets. Or, as you say, they aren't that expensive so just bung a new one on.

Agreed with Gilbert.