Restricting births, killing the elderly, spending efficiently, funding better - All things that are either not going to happen, or are completely ridiculous suggestions. Limiting numbers on immigration is realistic however, as is making a more efficient and healthy society, as well as training home-grown citizens to work within its health service. I really don't understand why people aren't getting this.
You can argue net migration will go down, I can just as easily argue it will go up. No one can predict the future. The Ukraine war or Hong Kong can happen in different forms, alternative disasters could occur, or political changes could mean anything. The UK is still a desirable place to come to and it could very likely swing upwards as well as stay the same, or go down. As the global population rises, they'll be a natural inflation as well. It isn't really the point though. Even using averages, the UK population will nearly double in the average lifetime, it is fucking crazy to suggest that this won't impact the health service the way it is going.