Hi Simon, and welcome to the forum community.
Before you start in on paperwork, I think it would be best if you planned your route.
There are a few "no-go" areas between where you are now (Saudi Arabia) and where you want to end up (UK). For example, Iraq and Syria. This means you might eventually decide to ride into Jordan and from there into Israel (if that is possible, meaning, borders are open, etc.), then travel by ferry to Turkey or Greece and ride home from there. Another possible option might be Saudi - Egypt - Turkey.
I can't offer you any advice on route planning, but I am sure others can.
So far as paperwork (insurance, shipping, licencing, that kind of stuff) is concerned, we have a section here in our forum dedicated to that. If you go to the
main forum directory, then scroll down a bit, you'll see sub-forums dedicated to Route Planning, Transportation (implies ferries, etc.), and Trip Paperwork.
Have a look at those sub-forums, do the research needed to plan a tentative route, but don't start in on investigating paperwork (insurance, visas, carnets, etc.) until you have firmed up your route.
You might discover later in the process that paperwork requirements for some countries along the way might be so onerous or expensive (carnets come to mind) that you would be best off to skip those countries altogether, which will lead you to re-iterate your route.
Lastly, keep an open mind to the possibility of just air-shipping the bike from Saudi Arabia to Turkey, and starting off from Turkey. Air freight is not cheap, but it would probably cost less than what all your per diem expenses, insurance expenses, and operating expenses would be if you rode from Saudi Arabia to Turkey. Not to mention that it will be fecking hot riding in Saudi Arabia in the summertime - you will need to buy a lot of expensive and specialized clothing and equipment to make a long-distance trip like that across the sandbox in the summer.
Michael