Well I put my mouth where my mouse was and spent some time tonight rolling backwards and forward at the exit to the start point of regulator where the grey pathway leads out into the open air. To be honest I was pretty ho hum about it all but using Chris's benches and thoughts as a guide and down scaling for an FX I managed to get the following
1) I got rid of the 3 bands of textures going away from me by applying quality settings and going from bilinear to trilinear.
2) I further smoothed it out by going to 2x ansio .
Result is a lot better IQ with acceptable frame rate loss.
So thanks Chris, you managed to get one guy off his lazy butt to actually improve his game playing experience.
PS Sadly though if I get indoors again I am going to be fiddling for another hour as I have to rejig everything on a different level damn variations