Got one from 928GT in the States that they had on special offer (last one) along with a drier receiver for four hundred bucks delivered. Customs was £40 so all in all about £240, not a bad price for a condenser and drier/receiver. Furthermore, after it was delivered this morning Mark Henderson (great aircon guy who works Stirling/Glasgow and around) came this afternoon with his sidekick and, after tea and sarnies, had the system working again a couple of hours later. He had to fit a new low pressure switch and improvise a high pressure switch at the top of the reciever drier as the original had packed in and he didn't have a replacement (would also have had to depressurise the system and then regas).
The aftermarket conditioner wasn't a perfect fit but it went in without too much aggravation, and there is the added bonus that it is made of copper so, according to Mark, will last longer than the car... Nice cold aircon now. I'm a bit gobsmacked this is working on a 1986 car! And all because I thought I'd try fitting a belt to the compressor to see if it was working. Now to get the cruise working again...
For those struggling to find one in this country the one I got looks like the one here:
http://cpwstore.carpartswholesale.com/catalog/?N=11566+1698+4294966975+9171
I'm pretty sure it is the same as mine but they have swapped the image left to right (the pipes should be on the left) and I should say the same picture is used for the 87 onwards listing so a bit of care required here. During my trawl of American sites these ACI condensers came up on quite a few of the large American wholesalers -- just a matter of finding one who ships abroad at a reasonable combined price. The alternative is the £370 Porsche part. I'll say this though, the yanks are pretty good at getting back to you with shipping costs for abroad; they seem to be used to supplying costs and doing the shipping.