New (old) alternator fitted this evening and all the systems are back up and running. Hard gear shift was caused by the high voltage. Charging voltage now 14.5v. Simple to replace alternator.
Just the gear interlock which is stuck now so need to sort this out.

 

Good update, does it click when you depress the brake pedal? Some have removed the brake pedal switch and cleaned the switches with contact cleaner, others replace the interlock solenoid on the side of the selector under the ski slope, you've to find out which!
Also can you select all gears without issue once unlocked? (selector/cable alignment Q)

 

It does not click. It used to take a couple of taps with gearshift before it would click the solenoid but not now. All gears seems to work once manual release is used.
Best I have a go at brake switch first. Brakes are a bit spongy but this should not affect the solenoid?

 

The solenoid or brake switch have nothing to do with pedal pressure. The brakes might benefit from a brake system bleed - with an Ezebleed it's dead simple. The pedal can be really improved with braded hoses.