I think the issues are more to do with the type of "tradesmen", usually caravan enthusiasts, which offer their services in this area. You will find exactly the same issues with tarmac if you look at sone drives.
As above, all in the prep.
Used them on this job for someone as log cabin base. Can be hard to knock the spikes in to the hard-core but if one or two break off not the end of the world as they all interlock anyway.
What did you pay out of interest? Small bits of kit like these are normally a great earner for the companies % wise.
Wouldn't go back to hand nailing would you...
I couldn't get for this place but is definatley the way forward. Think there's a bit more wastage and bit of waiting time but if you have a dumpy of sand and few cement on site for blockwork to avoid dead starts.
I undercut all around and foam in with inbetween fitting. Easier and better job IMO.
I use foil tape if I have to do pir over top of joists/rafters. In my layman brain it completes the foil vapour barrier.
Re spec what kind of thickness back panels do these German have? One point with UK suppliers DIY are the only company who seem to supply full thickness 18mm back panels.
Its not the be all and end all just a genuine difference I thought worthy of mention.