Yes, if it was shared then he has a right to it.
He needs to write and ask for access to get his share or say he will go to Court and seek a Court order.
If she refuses then he has a choice. Sue for half the cost (which may be cheaper) or seek an Order making him get half.
If she refuses then he can seek a court order.
He would need to issue proceedings using form N1:
If its just the money element he can do that online at: www.moneyclaim.gov.uk
But if he wants access he will need form N1 and he cant do that online.
The Court will issue the claim then send a copy to her.
Depending on whether she admits it the matter could be set down for a hearing
Can I clarify anything for you about this today please?