IANAL, all this is just my opinion.
Speak to your neighbours to see if anything was delivered. See if you can speak to a human at PayPal.
If you funded the PayPal payment using a Visa or Mastercard card (any card, not just a credit card) and you don't get sense from PayPal then try a 'card chargeback' (not a Section 75 claim) with your card provider for the payment. This should wake up PayPal and the vendor.
Even then you are not out of legal avenues. The next step will be the County Court, if it's worth it.
At this stage they are in the position of only having to prove things to their satisfaction. You can go through the same steps as above but, ultimately, if they or PayPal will not be more reasonable then, again, you can take it to the County Court.
In the County Court, actual evidence is required to persuade the judge and the case is decided on the balance of probabilities. Judges have very likely had poor experiences with Hermes too.
Not that I am suggesting that you should take it to the County Court except as a last resort. The County Court has costs associated with it. But it is the ultimate destination if you cannot get sense out of the vendor, or Hermes, or PayPal.
Certainly my next port of call in your situation would be to try phoning and speaking to a real human at PayPal for both cases.
P.S. I am jumping the gun a bit (since County Court action should be a last resort) but if you do need to eventually go the County Court route then get this book and follow it: 'Small Claims Procedure in the County Court'. It tells you everything you need to know, including about pre-action protocols which are now important for all claimants.