Thanks for the reply mate, I took it out today and they seem to work at the position I have them set, in fact they are
really comfy and sit a little higher than the old ones so happy with them now I've got my head around them not being fixed upright... I had imagined the passenger seat flopping forward every time I braked, but then I remembered this is a Land Rover...
I looked at fitting the centre seat in the way you described but I can't seem to get them close enough, and my mild OCD is nagging at me to get it all level LOL so I think I will fabricate something... I can weld an extension piece to the centre seat belt brackets easy enough to fit the back to and make up a frame for the base to sit into so that sits higher - doesn't look like too much work tbh and then it will all sit level and my OCD will be happy! I'll post a picture when I've finished.
Thanks again.