After trying reversing the magnet in the neck pickup but not reversing the pickup itself (so that it appeared as normal) I found the out of phase sound to be a little half hearted, so I reversed the pickup (as per Peter Green's). The effect was dramatic to say the least, the neck pickup became super loud because of the placement of the poll pieces I'm guessing, so I had to screw down the neck pickup and raise the bridge one. That had the desired effect but I still didn't sound like Peter Green, I can't think why☺️
The problems that I had with this mod, is when using the middle out of phase position it was a great deal quieter than when using individual pickups and as I wanted to use the out of phase sound for lead work, setting the levels for band practice just became a massive juggling act. I've now reverted the guitar back to it's original set-up.