You can always obtain his contact number should you wish to call him. It's available via eBay.
Enter the transaction number and eBay ID then you will be sent an email with his phone number. He will get one with yours too! It only works if you've had a transaction with the member though, in this case your fine.
At least then you can give him a call. Sounds like he wanted more for it then it sold for so has said this to you, else being reasonable he'd have called you to apologise. If you've paid a deposit you should be able to get that returned via PayPal again call them once you want to go down that route.
Don't worry about a strike. If he needs to cancel the sale tell him to send you a mutual cancellation form for you to legally withdraw from the purchase. Your still able to neg him if you choose, up to you. He cannot neg you regardless.
Hope it helps, let me know if you need contact number for eBay/PayPal
Peter @ Boatsandoutboards4sale ~ firstname.lastname@example.org
~ 07930 421007