Well, after much faffing around with various prototypes I have the final design for the functioning (the ones powered by the turnout motor) tie bars.

Basically one independent bar for each switch linked underneath by a springy brass wire allowing some sideways movement as the bars move towards each other as the switches throw.

I have cranked the wire clear of the end of one of the bars to allow for the drive pin from the motor. The bars are secured to the switch blades by the bent dressmaker's pin method, you can see the pin heads set into the back of the bars.

Right, Ambis cosmetic bars next