@jostro65 Just looking at your wheel system I wonder if using timing belt wheels may just improve the outcome a little. We have used timing belt wheels and belts as a drive mechanism if the access is tight.

@jostro65 The joys of a 3D printer..! 😀

Couple of small pulley wheels 3d printed with press fit onto rudder shaft and screwed onto servo cog 🤞.
wouldn't have thought of this without your input guys so thanks to all again.

@jostro65 Here is the way a closed loop control works on the small EeZeBilts, which don't have much space either...

@RossM, again another simple way to address the problem that I hadn't thought of.
These now seem so simple that I feel foolish not even thinking of them, but it's a true saying that "you don't know what you don't know".
Thanks for taking the time to actually illustrate your solution as well, very much appreciated.
I think my first attempt will be the pulley option as I just started printing off a couple of parts on the 3d printer.
Guys thanks again to all who replied. 👍

This is only a mock up of an idea.

The black at the bottom is your rudder control horn, facing forward, no need to be facing sideways
The yellow represents cable or very strong string
The silver in 4 corners are eyebolts/eyescrews
The black at top is your servo, placed as far away as you need it to be placed

When the servo horn moves, it pulls the string/cable one way and releases it the other. Reverse the servo and reverse the direction

This is the kind of reply I'm looking for to help with my limited imagination. I'm used to using pre-built/assembled RC stuff so when things don't work I'm stuck!
I think the simple option is, as you've both suggested, a belt/pulley drive, possibly even a simple rubber band if possible.
I've been sitting on this for a while now whilst doing other stuff but I can now move forward with your help.
Much appreciated folks! 👌👌👌

That is indeed a tight space... I'd maybe look at a belt drive, a pair of pulleys and a toothed belt, and you then either create a 'pseudo' rudder shaft a bit further forward, Or mount the driving pulley directly to a micro servos splines. Given you have a 3D printer you may be able to create a 3D printed pulley that mounts directly to the servos splines.

Or on a similar line of thought, a couple of conventional, maybe 3D printed gears that would allow the servo to mount just forward of the rudder shaft, the gears mesh and you have your control....

I use Motionco for these kind of parts, they have a calculator too to work out centre distances between pulleys. https://motionco.co.uk/aluminium-pulley-bore-p-729.html

I can think of a couple of methods. I attribute all of these to others with more imagination than .
1)Use a chain and sprocket system.
2) Use a cable and pulley system
3) ( I like this on the best) Using miniature miter gears, one on the rudder shaft, the other horizontally mounted to a sideways mounted servo