Not sure why you’d ask Motability customer services in regards to non-refundable deposits or cancellation fees, since both are asked for by the dealership and not Motability.
They’ll tell you to ask the dealership. In fact, they even state it on their website.
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.