yeah the guy in my local pnuematic supplier couldnt find anything off the shelf. its nearly M8 but not quite.
as Jonathan says its probably "M8 fine" but as i do not have any thread gauges so i carnt be sure.
i dont have a lathe that will do screw threading bit if it comes to it i will have take it apart and drill it out and re tap it 1/8 BSP.