Davidjames23; "All of my life, when doing a course, I spent my time studying much harder (and longer) than many of my contemporaries. My exam results have never reflected this. Other people always seemed to end up with the better grades and me with the average or failing ones! I know there is a big difference between working harder and working smarter but I have never managed it."

Davidjames23 you are in good company. There was a man in England who found himself in the same predicament as you. The more he studied the longer he studied the less he learned and he got average or failing grades. This man's name is Tony Buzan. Tony Buzan has spent his life learning how the brain works and how people learn. I strongly recommend you read his book the Mind Map book.

"Speed reading has been a particular problem for me and I haven’t yet managed to break the habit of sub-vocalisation." Photoreading is not speedreading. Speedreading is simply moving your eyeballs rapidly across the page. Photoreading is mentally photographing 1 to 2 pages a second exposing the book to the other than conscious mind by changing your field of vision by using your peripheral vision and bringing the material you photoread to conscious awareness by activation techniques.

"At the age of 40 I want to go back to beginning and learn how to learn from the ground up to prove to myself that I CAN really tap into what I hope is a huge ability to learn."

You have that ability to learn. It is innate. You were born with it. Now it is about applying the right techniques so you can get the results you seeks.
Photoread4me