Subsidized to Private Insurance Advice

​Hi everyone, seeking some advice on a surgery/insurance situation.

​1. I'm scheduled for surgery on an incidental finding in NUH, it was an internal referral from A&E to specialist. This happened in 2025. All in the subsidized route. 2. I'm asking to move to private route. Appointment is scheduled end of Jan and surgery in later date. 3. During which time, my employer's insurance switched to another insurance firm and they indicate this may be considered as pre existing. 4. I also have a private insurance, but would like to minimise any out of pocket if possible.

Do I need to get a fresh referral letter from GP to private NUH, for insurance claim sake?

My worry is my employer's insurance won't cover citing pre existing.