OP says he doesn't have the money, you say he is deliberately withholding it, those are two completely different things.
First things first. I have ignored what the seller has SAID. I have looked at his actions to deduce his intentions. I think you have done the opposite. You have taken on board more what the seller is saying regardless of the facts of the case (ie the actions)
I already provided evidence of suspicious behaviour by the seller that would lead one to believe (using common sense) that something was not quite right that warranted a criminal investigation to clear things up.
Like ive said, ive stuck to the actions involved, not the various excuses (by the seller) that have been mentioned. Why? because in this context his words dont count for much ie they dont clear him, only his actions can damn him or rather prove to us what his intentions are.
Thus far the "seller" has sold nothing to the OP and yet has managed to gain £1k+ of the OP's money. He has also managed to keep this money despite not being able to provide what the OP paid for. (and yet some still think he's a legit business person...impressive)
Now if the seller had refunded the OP straightaway or said yeah he would within a couple of days (and it went through) then that to me is the legit normal thing to do. The fact that the seller now wants to pay in installments and doesnt want to reveal his address should send alarm bells ringing in even the most dense of individuals Energize.
When all is said and done EVEN IF the truth is the seller messed up financially which is why he doesnt have the tickets OR the OP's money then at the moment he is trying to cover himself and at the very least he has defrauded the OP out of his money (by his
negligent actions) and imo the OP is quite within his rights to report him to the police.
I'm curious what kind of evidence would you regard as being proof of his dishonest intent? As you claim there is none so far.