Ford KA banging noise when reversing, full lock

If they can't get car to do fault , it is hard to diagnose .If it only does it first thing ,you would have to leave car overnight with them to see if it showed up . Going by year ,take it repairs being carried out under warranty ? Really have to let them replace bearings if they think possible cause , something might show up on dismantling .They would already have already checked steering , suspension , exhaust etc . for any excessive movement I assume ? If still having probs after Tues. repair , come back to board and will try and help / advise.

Ford have already had the car overnight, in fact they've had it for several nights! They also sent an engineer to my house early one morning to hear the noise, we did eventually manage to get the car to perform! The work is being done under warranty so at least i'm not paying, although I am paying for the courtesy car and CDW each time they have it. I will obviously let them have a go at fixing it on Tuesday, maybe it'll work! I originally posted to see if anyone had had a similar problem. Thank you for your reply, I'll let you know how it gets on!

Well, Ford had the car on Tuesday and Wednesday.
Thursday morning I got in and reversed - "CLONK". No difference whatsoever :o(
So, another lovely man from Ford came to my house at 7.30 this morning, took my car away with him and left me with a practically identical one.
The idea os, I'll drive the replacement for a few days and see if that one makes the same noise, for some reason Ford seem to think the problem is either me or my driveway! even though the noise has happened at places other than on my drive and with people other than me driving it!
All I want is my new car to work properly, is that too much to ask?
How many times do I let Ford have the car back, with all the inconvenience and expense that means to me, before I insist on a new car altogether?