That's a shade of the old arrogance you accuse London of having.
What sort of deal will we get? They're refusing to negotiate until Article 50 has been executed and they have ruled out access to the one market without membership or accepting the rules. Seems like they are playing hardball and that's expected. They have said we won't be allowed to pick and choose the rules. But if such a deal is possible, what's stopping other members from threatening to leave and getting similar deals that are tailored for their own requirements? That's something else they have to worry about so I wouldn't be surprised they they try to come down on us hard to discourage anyone else from leaving.
Now is it not possible that with us leaving and losing money, another major city benefits from what we've lost? What if one of these major banks decides to move to Germany or France? What if inflation goes up, taxes go up and we can't even afford to buy German cars? Many have said it's not in their interest to cut off their nose to spite their face but it's looking like a lose lose situation for the EU unless we actually don't leave.
Heck, we may even see a scenario where we see EU reform to save itself but keep us kicked out.
They really don't like our arrogance.