I am surprised they're surprised.
Would be interested what price range you surveyed - for example new and £10k-30k might be 40% down; but is £2k-£4k down too?
Regarding the UK, I suspect there will be a proportion of dealers who will do everything they can to NOT open in the near future, given that they will probably lose money at a higher rate than they are currently, especially with the majority of their sales team furloughed. I think the only ones which stand a chance are those which were either 90-100% of the way there with online selling (as in, reducing the customer contact to 0 visits or 1 visit to finalise everything and collect it). You'd have taken the risk to invest in the internet tech pre-lockdown and that risk will reward you well now.
Also I reckon most people who simply "wanted" (didn't NEED) a car before, don't want it now. And a good proportion of those who needed one before don't need it any more, at least for the next few months ( household 2>1 car, or lost job, or try fix broken car).