I am very impressed by that site, fullfact.org.uk. I did think though that we'd made ourselves unpopular by vetoing legislation, especially the sort giving welfare and employment rights along with environmental protection. Sorry, don't have details at my fingertips.
I'm interested in the difference in European thinking that tries to make life better for the disadvantaged. For instance the legislation that has made facilities for the disabled mandatory. This may seem like wandering away from the central Brexit question, but, in Stockholm last year I was stunned to see so many people in wheelchairs out and about, to see how buses and street furniture is adapted for the disabled (and thus for mother's with buggies, the elderly with walkers etc). Most amazing of all was waiting in a queue for a bus, the queue was a mix of old and young, able and disabled and when the bus came, the disabled and less able were happily allowed on first with no hurry or angst.
I think this is the sort of thing that needs to be led from the top down and my experience of the UK is that there is increasing privatisation, decreasing provision of public facilities and caring for the less able and disabled is always 'too expensive'. So I suppose I am grateful to the EU for what membership has brought and what has seemed like a dragging along of the UK Parliament into a kinder world. An ex neighbour of mine, elderly herself but rather well off and very anti EU has ranted at length to me about 'the money spent on changing infrastructure and how many people in wheelchairs do you see about then, day to day' she'd say, thrusting her face in mine. Very ugly.
So from what I've read, I don't believe our sovereignty is really threatened but I do think we need to cooperate with other governments, it's not just about trade and money, and I think we can learn from our European neighbours how to allocate resources for the benefit of all. In my lifetime I have felt the EU has been proactive in this. Sorry if this seems like a long post. 