I have a new VHF, a Standard Horizon 1850GPS with an additional handset (RAM4) for use at the wheel. I plan to have the connection right under the traveller as that is a flat, more or less protected area. The question is how the cable can best be routed. The RAM4 comes with a 7m cable with fixed connectors on either side. The smallest connector measures 18mm.
My idea was to try to push a drawing spring from under kitchen sink (as there I see the large black cable bundle as well as the heating duct) to the space near to the calorifier and the fuel tank.
Does anyone have experience routing a cable this way? Perhaps someone has a better suggestion?

I fitted a vhf handset to the side of the helm pod. But my helm pod could be larger than yours.
The cable went up the stainless tube of the wheel support. I think you have to remove the plastic end connector to get it up the tube.

The route described - back of instrument panel, battery box, sink, follow the heater duct, through the cockpit sole up the pod support etc - sounds right. Like Mike, I went up (one of the two) stainless steel pod/wheel supports. However, mine are now jam full. I've often thought about having a mic for the fixed VHF DSC set (better range than the handheld) at the helm, but I think it will require a different route and more £££ 😢

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Well, I managed to route the extention cable for the vhf remote from the nav station to the cockpit. It was indeed a nightmare as Ewan predicted, especially when doing it alone. But with his advice I bought an endoscopic camera at Amazon. It was indispensable ! I needed two drawing springs to reach the space below the kitchen sink from both sides. There I connected them and pulled the first spring through.
To pull the extension cable (and the spare line!) I used a device that’s called a ‘cable pulling sock’, that looks like a metal wire chinese finger. That was great as the cable was firmly attached and didn’t get stuck anywhere.
Thanks for all your advices!