Thanks for the reply.
I took the seat out yesterday and I'm glad to say I found the issue and have resolved the play that was in the seat.
As it turns out the movement was a back and forth motion and after flipping the seat upside down so I could see the bottom of the runners I found that it was moving where the locking mechanism attaches to the upper seat runner via 2 bolts. One of the bolts was slightly loose, so all I had to do was tighten it.
I've attached 2 images to show where the bolt is situated under the runner just in case anyone experiences the same issue in the future. No more loose seat!
For anyone reading this with the same issue here's a few things that I wondered whilst removing the seat and answered for myself:
- I disconnected the battery but was wary at first as I was worried that it would reset the key. After reconnecting the battery, once the seat was back in and all the leads under the seat were connected, everything worked absolutely fine. All I needed to do was reset the clock and the one touch on the electric windows. I also have an after market stereo so I'm not sure if a standard radio would need resetting at all.
- When I undid the rear torx bolts holding the seat in it felt like the nut holding the bolt in was very loose and would tighten up again properly. As it turns out it was fine and is only loose once most of the bolt is out. It's housing keeps it in place so it can't move when you do it back up.
I hope this can help some one else.