[MA70-3.0GT]

Yeah that's what I thought from the cutaway pic, still there was some hope there...

There's no obvious cross-contamination of oil/coolant although a small amount could well be getting transferred.

I'm more or less 100% it's BHG now anyway as the coolant's started showing tiny flecks of silvery metallic & brown fibrous bits that look to my eye like tiny pieces of head gasket.

I'm going to do a chemical test if I can get hold of the stuff from my dad's work (I'm not paying for it now I'm convinced it's only gonna tell me one thing!) and if not then I'll just bite the bullet & start ripping the motor apart again. On the positive side, at least this'll give me a chance to see first hand how well the other work has been done.
The place is a reputable shop but I'm just thinking somebody (i.e. the guy who re-assembled it, who no longer works there... ) didn't realise how hard these things are to bleed properly & the resulting hotspot has caused the problem I'm now loaded with. Either that or the head's only torqued to 58, we'll see when it comes out in the wash. Anyway you look at it I'm ahead though, the new 17" wheels & tyres fitted are probably worth as much as a Pajero with no MoT or tax, so the way I look at it is I've got a sickly-engined but otherwise mint Supra (I'll post some pics up when I've washed & waxed her) thrown in free for good measure!

P.S. the bubbles were pretty much clear (mainly because I've not been wasting antifreeze on testing the car, was going to refill with proper cooland had the HG turned out OK). Just the consistency of them, small tight packed bubbles about 1mm or less in diameter, reminded me of Aero bars. I'm guessing you don't have the privilege of light bubbly chocolate in the U.S. unless under some other guise...