Yes, EU isnt a growth market for UK exports anymore. 44% is still a large number ("half").
What you'd actually look at is trade deficit. So how much more do you import than export? From a certain region. And then look at the same number on the EUs side (different countries). (Germnay afair will be hit most by Brexit on the EUs side btw)
Btw what innovations has the UK produced in the last 12 years? So thats the other side of the coin, if you have free trade - and you are not staying competitive, but are still a high wage economy - worth will leave your country.
Also - understand that everyone still wants a free market in some form (some sectors excluded maybe (protectionism)). So regardless of what that number is, you are not cutting ties there. You are not doing a hard brexit as far as I've come to understand..
Meaning the whole 'better deal' always actually was about 'getting sovereignty back' but thats solely to undercut your workers rights and regulations when dealing with poorer (but still likely to grow) countries. No one - and especially not the US want more regulation and workers rights than the EU essentially.
So its sovereignty over being able to turn down (reduce) rights and regulations when dealing with other countries (so to f.e. outcompete lets say italy in shoes - which is one of their main industries, which EU would have prevented), and at your own speed.
Thats the freedom you have gained. Look at small and medium enterprises in the labor sector. Their conditions should actually deteriorate, and not improve over the next few years. So whatever xenophobic motive ('more money for our people') people might have held there, they have voted against their interest actually.
And you made sure to vote in a very market liberal govenment on top of that, so yeah..
Good news is, that after the shock - you might grow your country 'better' to what it was where you left the EU (you exchanged better growth trends long term for worse economic conditions short term, and poorer working conditions). But predictions say thats starting maybe after five years - not short term.
And your national banks will pump in credit to lessen the short term impact (keep the pound strong), but you'll still feel it. (Recession, stagnation, ..)
Savings on EU projects is nothing compared to what has to be invested there. But that goes on top of your state deficit, so thats your long, long credit line - so impact can be negotiated politically (when you do something about that). It never was about the money you payed for EU projects. Comparatively those are peanuts. You get one new hospital in Bojos home town, and thats it.
To better health care for the (not so affluent) elderly is not a priority in a recession.
edit: And you are out of 'further integration projects within the EU' common banking system, common army, exchange system on higher education (private (work visas) and public) ... But you'll, still retain 'partner status' on those at least. Probably. To at least have an inside view of whats going on.