Paul, you absolutely MUST get those BG numbers down between 4.5-5.5. You are at a very dangerous, damaging level of chronic hyperglycemia. Also, as I don't need to tell you (your doctor I'm sure is hammering you about it) the BP numbers are very high risk as well.
What to do? First, try Humulin. Just the straight stuff. Same thing your body makes, so you should be able to take it. I don't know where it's available in the UK, but in the US it's available at Walmart for US$25/10ml bottle. If you can tolerate it, then this is the key to getting your BG under control.
Also, you can adapt your metabolism to run entirely ketogenic -- no carbs AT ALL. This is a perfectly healthy way to live, and there are lots of people doing it. Take a look at this article on ketoadaptation to get started on learning about it. It's a protein/fat based diet, so unless you're a vegetarian/vegan, you can eat all sorts of stuff that's yummy. Like bacon and eggs. The key is avoiding all carbs.
Your body still needs a small amount of glucose, which will be created by the liver from protein, mostly. This requires a little to no insulin. The reason why is because the few tissues that depend on glucose (chiefly neural and red blood cells) do not need insulin to absorb glucose.
Part of what is making your BP so high is the out of control hyperglycemia. I've been there. Get your BG in line, and keep it well controlled for 6-8 weeks, and your BP will come down. I was chronically running sugars in the same high range you are for quite a while, and my BP was concomitantly 180/140 or similar -- like you.
I did a 180, got my BG under control, and now 1 year later my BP is normal. Without any meds.
High BG also sends your cholesterol out of whack. While getting BG in line may not bring LDL/triglycerides to where they need to be for a diabetic, they'll come way down with good BG control.
Paul, your chronic hyperglycemia is a major contributing cause of many of your other issues. It's the key. You've got to focus on that, and that alone in the immediate moment, and tame it.
One more thing: You feel rotten below 8 because you are experience something called "false hypoglycemia". I went through that too. It's a result of your brain being bathed in syrup for so long, that's its used to it. Take it away, and it goes into withdrawal. Really. Acts like BG levels are getting dangerously low, even though there's no danger at all. This too will resolve in a week or two of having normal BG. You can either go the commando route like I did, slam the BG down to normal and just ride out the 3-4 days of false hypo, or do it gradually, bringing your BG down over a few weeks to normal, and pretty much avoid the false hypo thing altogether.
In summary, you are not without any options. Try plain old Humulin. If that's a problem, try keto-adaptation. And, like others have said, throw desensitization into the mix. Some combination of those 3 (human insulin, very low carb, desensitization) can work.
At those BG and BP levels, friend, you're life is literally on the line.