I read in another thread that to remove this handle the button prises up and there is a nut underneath. I have tried pressure under the button to get to the nut and it seems reluctant to easily remove and give me access. Is there a trick to this or does it just require quite a bit of force?

Force on plastic = breakage!

Clips on the side (or front and back) that need gentle pushing in towards the centre, I believe.

exactly what MadMax said to do just be careful i use two tiny flat blade screw drivers and pushed them in the sides of the shifter from the top and gently and slowly pried the button out that way. Just take your time and look at what's happening as the button comes up you will see the two clips. Once you have done that then its simple to do remove the spring and the rubber thing and with a deep tube socket remove the nut holding the gear stick on and it will simply lift off

Got it out. A butter knife down each side (tight fit) and gentle pressure inwards as you said. The clips are part of the button. Underneath is a plastic frame fitting with three screws which also must be removed, then a spring and soft sleeve on the shaft removed to reveal the nut. Fortunately had a socket long enough to just reach it. Wonder why they made it more complicated compared to the TL which is just a single grub screw holding an all in one unit. Thanks very much Madmax and taniagirl! This forum is fantastic for quick answers for tricky problems.

Never needed to do this on a Magna, but it's marvelous what a quick look at the manual will tell you! lol

Couldn't see anything in the Haynes so glad you have another one. :)