Yes : take it into an independent bodyshop, and get a quote for getting it fixed.

But I've already advised that.

Three weeks is too long. Imagine if you sold a car privately, in good condition, and 3 weeks later the new owners came back, pointed out damage under the car, and insisted it must have been there from before you sold it. You'd tell them to do one, as they were obviously trying it on.

I will point out something else. Your wife took delivery of (I assume) her new car. Yet you've been driving it around town for 3 weeks.

In a lot of cases, you'll find it's the other driver who has caused the damage, and is just too embarrassed/afraid to admit it. So hell, why not say it must have been there from before you got it ?

This is the problem i don't think we are going to get anywhere with this and have been absolutely stitched up by the dealers!

The problem is that it is effectively your word against theirs, unless you can prove that the situation was not caused by damage from usage (whether by yourselves or those originally delivering it) - your only chance is that an independent inspection states that the 'damage' is caused by fault(s) in the manufacture of the car, which may be difficult given where the problems lie.

I had an issue with my car where the dealer found at service a plate under the car had been half sheared off - I didn't remember scraping anything (I am normally very careful) other than once or twice the front bumper on a high road hump, but I accepted that it was probably me that had caused it as opposed to the servicing agent (no road humps in the area and no other damage to indicate they had had an accident whilst giving the car its short 'test run' at the service. It may be that unless the 'bottoming out' is significant, you may not have noticed it.

Somehow I think you'll find it difficult to prove it was the dealer after the time elapsed - just bad luck you'll unfortunately have to endure and pay for the repairs.