First up I voted remain and would vote remain again (or even better revoke article 50), so I accept that my points have some bias in that direction - but I think that some of my thoughts are valid and would hopefully get some people to consider their position.
General EU ponderings
The first point is that the EU is not a perfect organisation, there is plenty of pointless waste - moving the parliament every 6 months or so is bloody ridiculous and must be stopped! It needs reforming, but that is difficult from the outside.
There are people in there pushing the political union idea too far too fast - this is likely to blow up on their face. For national identity to solidify you need more than monetary union (that was pushed too fast by Kohl and Mitterrand back in the 80s) and the Ryder Cup team to support - people across Europe aren't ready for that yet!
As far as I can tell National Identity is mainly focused on language, see the difficulties it can cause in the Northern Ireland assembly and elsewhere) - Europe doesn't have a common one, but English is taught as a second language in many places (that might be useful in the future).
I don't see a political union for Europe in my lifetime (so at least another 40years I hope) and a European army - well not until NATO disappears - which could be when the USA decides it doesn't serve a purpose for them. So I see these issues as scare-mongering by Euro-sceptics (is that like project fear?).
On the Euro-sceptics I genuinely believe that these people have held the UK back in getting the best from the EU, as they have caused successive UK governments to have weak and easy to isolate negotiating positions. If you start from "No" and offer nothing to those sympathetic to your position, I would guess that is pretty easy to out manoeuvre . (I feel some irony here with BJ currently complaining about the weakening his position with MPs trying to block No-Deal - Ho hum).
Trade
Keeping it simple - you do most of your trade close to home. Yes I could travel to Yorkshire from Devon to do a weekly shop, but the transport costs and environmental costs make that a rather silly thing to do. Yes we can trade with any country across the globe, but the closest will be the easiest. Have you seen the postage costs to and from Australia? Also being part of a big gang helps when dealing with big countries which are very self interested in themselves (think USA and China).
Borders
As far as I can tell the problem with the UK's borders is self inflicted. Having recent travelled to a couple of EU countries I noticed the following - a border guard scanned my passport on the way in AND on the way out. So I was counted in and out - clever that. However on UK part of the journeys the I noticed that the UK border force didn't check as l left the UK only on my return - so we aren't counting them in and out, only in. And what a surprise we don't know who or how many people are here (a recent ONS report). This is a choice of the UK government not the EU.
The Referendum
Now I accept that 17.4 million voted to leave the EU for many differing reasons - but how to leave was not clear and certainly not a mandate for No-Deal. The main issue I have with the result of the referendum is how it is used and its validity.
It was an Advisory referendum (- this is important!), so can be ignored by Parliament, as the UK is a Parliamentary democracy. Especially in the light of events since the referendum, such as the failing pound and lack of investment, so leaving will hurt.
There was rule breaking by both the Leave campaigns - this is FACT and the verdict of the Courts - this would invalidate the result of the Referendum result if it was binding - this requiring another vote. I don't think you can keep banging on about the Invalid result, unless you think that Ben Johnson and Lance Armstrong should get their titles back for breaking the rules!
I also have a rather snarky point about the public not really very good at making big decisions and giving the example of Joe Dolce's "Shaddap You Face" your face keeping Ultravox's "Vienna" off the number one spot for three weeks ....) - but it probably doesn't help my argument, but I think is quite amusing.
The Prorogation
This does stink of a tactic to prevent Parliament doing its job of keeping the government honest and working for the best interests of the people (although with the electoral system in the UK it doesn't usually do that particularly well - bring on Proportional Representation so people's votes count wherever they live! Sorry off topic there). So hopefully Parliament will be able to over turn this ploy - but I am not sure with the ineptitude shown so far this year by parliamentarians it is just hope.
Summary
I suppose looking at the last 300 years of Britain's history we have been at our most successfully when we are part of a Europe wide alliance - Marlborough (holding back Louis XIV), Pitt (Seven Years War), Wellington (defeating Napoleon) and Churchill (defeating Nazism) and least successful alone - the American War of Independence.
Even England's Kings knew that being in Europe was vital, Agincourt, Crecy and Spurs weren't fought to have less influence in Europe. So I don't understand the logic of removing ourselves from the rule making in Europe and the EU, it seems counter to what our great leaders of the past knew - you have to be in Europe to get the most out of it.
Overall the EU isn't perfect and is in need of reform, but on balance it is better to be in the the club, influencing it rather than on the outside looking in. Trading freely with your neighbours, with whom you have a shared history. Also the risk to the Union is too great and imagine how hard it is to pick apart 300+ years of union with Scotland, when you look at the problems we have got trying to unpicking 40+ years with the EU - it will hurt and be bitter if Scotland goes.
My thoughts on the shambles on UK politics.
Morts
