I spoke to motability today as im due to collect my new car in the next couple of weeks.
They told me some dealerships are still happy to handover cars if the customer is happy to do so but it will probably be done outside providing they have an ipad or something for us to type the pin into.
I spoke to my dealership (mitsubishi) and they have agreed for me to collect my car during lockdown.
Its worth checking with your individual dealership to find out