Sorry to hear that Steve - what a pain. There're a few ideas here you could try (the main ones you've already done unfortunately)
- Perform a Hard Reset: Turn the camera off, remove the battery, and hold the power button down for 30–60 seconds to discharge internal capacitors. Reinsert the battery and turn it on.
- Check the Eye Sensor: Dirt, dust, or moisture around the viewfinder eye sensor can cause it to falsely activate, turning off the LCD and turning on the viewfinder (which then blacks out if it's malfunctioning). Clean this area thoroughly.
- Re-initialize Settings: Go to MENU -> Setup (suitcase icon) -> Setting Reset -> Initialize.
- Check Zoom Functionality: If the zoom is erratic, the camera may be struggling with mechanical tension. Some users have found success by performing zoom actions while pointing the camera straight up or straight down to reduce stress on the internal lens motor.
- Try "Heat" Method: One user reported that using a hair dryer to gently warm the shutter button/lens area resolved a similar, persistent zooming malfunction.
The last repair I had done (on a Sony A6700) was by AJ Johnstone in Glasgow - they were very busy so it wasn't super quick but I thought they did a decent job.
Good luck!