Update.
I got the other two servos working with the DCC accessory controller. All three are now working. They are usually controlled by DCC commands. I also have push buttons to throw them. I've actually got two push buttons for each. One panel of two buttons is next to the crossover and the other panel with two buttons is adjacent to the siding turnout. This means I can throw the both the crossover and the siding from both locations without having to walk from one to the other. I like it a lot. This is an temporary solution, which, with a software update will be able to be switched to a new system
I needed to get the double slip installed in Emble June. motorised. No point putting the car door locking motors back in or more DCC Accessory controllers. It was time to start installing a Layout Control Bus on Amblethorpe and transition away from DCC for controlling accessories.
I've converted my tramway over to a Layout Control Bus last year, and have started installing one on ems mates layout. This means I'm familiar with the electronics side. The bigger challenge was getting a 10 meter cable out from my controlling Raspberry Pi to Emble June and installing the servo linking mechanism.
The install went better than I expected. One of the servo linkages took a bit of time to get throwing, but the other there went in simply. I had and issue with voltage drop which mean there wasn't enough power and the Arduino switched off and on. One of the servos was working too hard. An adjustment to it's settings sorted the problem. But I think voltage drop will be a recurring problem. I'll probably change from 5volts to 12 and put in a 5v regulator on each node on my layout control bus.
It's all installed under the baseboard. I'll find out how it deals with the outdoors. A plastic food tray is offering the electronics some protection. The whole setup cost less than £20 so replacing a component or two isn't going to break the bank.