Ok guys I'll tell you what I did.
I discovered by accident that Gear4music do what is called the LA bass for about 90 quid, it comes with a rosewood neck which I hate but I bought one anyway to see how bad it was. Imagine my surprise when it arrived and it was as light as a feather! When I checked the spec' the bodies are made of Paulownia wood which is very light so I wondered if they had a maple neck that was also 61mm. They had so I bought one to try out and it fitted! very tight but some very light sanding made it fit spot on.
There was a little neck dive, nothing much so I bought some wilkinson schaller stylee tuners which fixed it. I bought a loom from John (KiOgon) and a pickup of choice to finish it and it's brilliant.
Issues with doing this job.
The first one I did the neck wasn't exactly straight and the strings ran off a bit but it was easily fixed by using a Schaller 2000 bridge that has lateral adjustment so the strings could be lined up exactly. There are other cheaper ways to sort that though.
The fret edges can be a bit sharp but that's easily filed and smoothed, also the maple necks are a bit paddle shaped, my friend Dave on here very kindly made me a headstock template so shaping it was just a jigsaw and a bit of sandpaper away.
I'm very pleased with my cheap lightweight basses, my gas is now satisfied.
HTH
Tom.
Oh the necks are only £35