Dave blue I wouldn’t jump the gun with any deposit or hold but have a word with dealer making sure he will sell to Motability and that he will hold on until it’s all sorted on Monday also if it’s not nearby, that he will take order over the phone encourage him that the grants team will be involved, that way you can call the grants team on Monday and get it all sorted the cancellation of old order and instigation of new, will be quickly done for you I am sure.
good luck and keep us all informed
I am the carer / driver for my wife who cannot drive due to disability