Having done a bit of delving around a couple of other forums, it appears that both Dunlop (D250) and Avon (AV72) now make a 180/60-16 (for Wings and Hardly-MovingSons) that will go in the back of the Paso without any fuss.
Not sure about this myself, but if anyone has tried it i’d be interested to hear the results. 
Avon still list a couple of options in 150/80 size, which I modified my 906 to take in conjunction with a 130/70 front.
Does this mean I can get a tyre now for mine ??
We can have a chat about it at Stafford I hope, just putting new rear pads and caliper seals in as well.
Don’t know yet. We can ask a couple of the tyre people at Stafford and maybe take some measurements.
My avons will be here Friday, 130 70 front and 150 80 rear, not the white wall option !!
Bloody hell, chain lengthen, mud guard off being modified, leans way over on side stand, what an arse to do. Now for a ride, lets hope corners are not the adventure they were.
Pay the 180 at Sammy Millers, looked big with no obvious mod, I have the 150 which handles great.
OK, more news on the tyre front and it is all good, Pat Alexander, club member and user of 851 888 forum has tracked down a company that are making the tyres again, great news.
Link is here
There is a bit of modding needed. The front sprocket can simply be reversed, but to space out the rear sprocket it needs a spacer making up to distance the hub (which bolts to the rear wheel) out by (I think) 10mm. That pretty much does (he says with no idea of the consequences!)