So after some playing around with flexitrack and standard turnouts I have come to the conclusion that fully handbuilt is the way to go at least for the points! It's been a while to say the least since I used Templot, but managed a first go at roughing out a plan last night.
As you can see all I've done is overlay some OO track over the N (for 00-9) so far. need some help I think from @martin_wynne to create some turnout templates with a small enough radius and large enough crossing angle for my purposes. That will come later. The section of dual gauge is far too tight, I'll need to break it up into sections so I can ease that curve. Will mean that the rest of the loop will be tighter but the NG stock can take it!.
Next steps? I want a stub siding where the "a" is on the plan, will be fun fitting that in but I need somewhere to park a standard gauge loco for shunting purposes.