Thanks for all the replies, lots of useful information.
I've had a good look under the back end this afternoon after work, because I hadn't done so previously.
As far as I can see there appears to be no damage to the actual tow bar, it's not bent nor can I see any movement in the fixings underneath. It's sort of an illusion caused by the bent plate and cycle carrier frame that's bolted on.
The bumper has definitely moved forward mainly on the off side. The tailgate seems to have been pushed forward at the lower edge, where the plastic trim is fixed on, possibly causing it to bend slightly.
I've actually got a complete spare tailgate in hff Green which I bought from a local breakers last year. I was intending to fit it because mine is rusting at the top edge, where there had been damage before I bought it. Just never got round to it.
Ironically we're still waiting on the special order new rear number plate that fell off a couple weeks ago on the M5!
Admiral have referred us to Auxilis and closed the claim but said it can be reopened at our discretion.
The man at Auxilus was apparently quite appreciative about the 75s and commented on their quality and decent engine, but said the company wouldn't entertain fixing it.
We can now get Admiral to look into it.
Or go with the people appointed by Hastings. The van driver has confirmed he had contacted Hastings. So this 3rd party lot appear genuine.
My wife had "we buy any old car" value it at £180....