Firstly I will congratulate you on your weather - it's raining here, so I have all the time in the world.
Given our current politicians, I think that we would be on a hiding to nothing if they had decided to go for a customs union. They weren't capable of putting their foot down when required and playing hardball, nor do I think they have the ability or the desire to stand up to the EU and negotiate anything for our benefit. It's the price you pay for putting the future in the hands of a group who profoundly disagree with the instructions of the referendum. My personal view is that we either get out properly, or stay in with a voice in order to mitigate the backlash. A customs union will tie our hands and give us nothing. I therefore still think the preferred option is to leave with no deal whether they like it or not. IF we end up with another referendum (which would be a travesty and presumably would have a predetermined outcome in case we were stupid enough to vote the same way), then if they really want to have any chance of closure, it will be imperative that no deal, remain or half-way house are all on the ballot paper. But I doubt they would have that wisdom.
The EU has moved their institutions back to the mainland as is their right. They will certainly move to get as much of the financial sector moved to Paris or Frankfurt whether we stay or not. If the only options are a customs union or remaining, then it is also a case of accepting that we will continue to get a bad deal from Brussels, at which point we would be better in being the least bad option, but I wouldn't hold out any hope of them investing any EU funding or infrastructure in this country again. The old adage of keep your friends close and your enemies closer was never more appropriate. To fully extricate ourselves will probably require a new political party with both the desire and the balls to make it work.
This undercurrent of discontent is a 46 year project in the making. For all bar one of these years (1974), we have paid in more than we have taken out. In that time, we have lost much of the infrastructure which would give us the ability to stand on our own two feet. Any other country would expect some sort of return for paying in, but we haven't really gained anything of substance in that time. I don't have a problem being a net contributor on occasion, but it does have to be offset on others by actually receiving benefits. In any system there are winners and losers, it's just that 17.4 million see no benefit, whilst only 16.1 million thought they were better off.
Our problems are to some extent home grown because our politicians are too ideological, unlike the majority of the population who are generally middle of the road and value a good social policy but crucially recognise that it has to be paid for. Too many on both sides only see one half of the story. The Tories are called the 'nasty party' because they are perceived to be indifferent to social policy, whilst the Labour party is mainly concerned with taxing and spending money on benefits without expecting anything in return, living in cloud cuckoo land that you can turn on the spending tap at will without ever questioning whether wealth is being or can be generated. The system is broken, but given we all place a value on wealth and it pays for all consumption, you have to make it to spend it.
So the question is, where should our priorities lie? The EU won't come riding to our rescue because we are only ever net contributors to the system, and going forward will be seeking even more from us. That is why a customs union is not a good idea.