So, I let him leave the car here after coming to use my tools and being unable to fix the problem by 9.30 on NYE with a party to be going to. That makes me a mug?
Lets explore the options..
Tell your friend that no, even though they know that you have a garage and a full range of tools that they can't come round and fix their car.
Continue to work on the car through into the new year even though there is little to no hope of fixing it without a proper new part from Ford. Both miss NY celebrations.
Send your friend off to try to nurse a car 15 miles while majorly haemorrhaging coolant, they will miss NY celebration at the side of the road with a broken down car.
Call it a day, leave their car on the drive, both head off to NY party in my car and good times are had by all...
Which of those would YOU choose, considering the final one makes you a total mug...