That is not correct, thier webiste states cars come with a spare key and they will siupply one if it is missing, it was also one of thier PDI checks.
Motorpoint Quality Standard | Motorpoint
Just looked at the above document and to me it just looks like weasley words.
If these items are not available on the day of collection, we will endeavour to get these to you within 30 days.
"These items" includes spare key (I prefer to call it the 2nd key) but what stands out to me the 30 day limit. Under the Consumer Rights Act 2015 your rights to a full refund change after 30 days, if there is no 2nd key after this time a rejection since the car was not as described would cost the buyer money since the seller is legally entitled to charge for the use of the vehicle and any charges would no doubt be greater than the cost of a key.
And the use of the word
"endeavour" is also clear enough. It means "to try" in a dictionary definition and no more, its not a promise to get a 2nd key.
But what is clear from the Motorpoint document is what they don't say which is what they will do if after "endeavouring" to find the key for 30 days, what do they do after. The document will have been written by legal experts and they know its not an open ended time scale. No key after 30 days and you can forget it.
So buy from Motorpoint with confidence (we had our car for over 6 trouble free years and saved £3000 over the local dealer price when we bought it) but don't take it as read you will get a 2nd key if its not there when you collect.