I have a whole host of eye diseases and spend masses of time with specialists looking into my eyes and conversing with others similarly afflicted with the same rare disease.
At Moorfields, they should be able to detect the presence of an auto immune disease through their examination of your eye, especially the back part. If they didn't dilate your pupils to conduct an exam of the back of your eyes, go back. I would be surprised if they hadn't done this as a matter of course. Their examination would also determine the presence of cataracts and the very first signs of cataract. The best time to go back is when your vision is foggy.
If you were experiencing ocular migraines, you would also see jagged lines around your vision as well as a blur in your central vision . It's fairly spectacular and not easily confused with something else.
A really simple cause of blurred, foggy vision which clears with blinking is dry eyes. They can do a very simple test for this at Moorfields. All that's needed to put this right is artificial tears, just make sure they prescibe the preservative free variety. Another cause of transient blurred vision is high optical pressure. Did they check your eye pressures at Moorfields?
In your shoes, I'd go back to Moorfields and keep going back until an explanation is given. Another thing to consider is the side effects of common drugs you may be taking. If you are taking anything, read the patient leaflets and you may find a side effect causing blurred vision.
An eye doc once said to me that they can see the presence of other diseases when they examine eyes. Sight is precious: you need to find the cause before you experiment with alternative treatments, guessing at what's wrong. Supplementing with selenium, for example, can cause high optical pressure.