L4/L5 herniated disc, tear on disc above and below?

Daz, to the best of my knowledge no one is doing multilevel disc replacements. At this time they will only do 1 and that is if the discs above or below are ok. In your case I am not sure what they would do. As for a 4 level fusion, that will place a lot of stress on L1. That level is not made for the kind of stress that it would have to take. If you are in the UK I don't know of anything over there so you would have to do some research as to what is available.