Double excess on insurance claim

Hi all,

On the way back from a very enjoyable weekend at bopeep in Oxford, our driver  side wheel detached and ripped a hole in the side of our caravan.  Which was bad enough. But unfortunately,  the third party recovery company (supplied by Greenflag/The Caravan Club) that recovered my caravan, caused more damage to the A-frame, ockey wheel and rear steady leg.

The Craven Club iinsurance company are trying to charge me two lots of excess. One on the initial damage caused by the wheel comming off and a second lot for the damage caused by the recovery company. They are also saying, they can't pursue the recovery company, as there are no witnesses. 

Can anyone give me advice on where to go with this?  As I think this should be classed as one incedent. As the damage caused by the recovery, is a direct result of the initial accident with the wheel detaching.

Thanks

Graham