That’s asking How long is a piece of string😂
Say about £1500 if you want to turn right about £8,000 in business.
It depends when you want to go but will involve a stop somewhere on the way so decide if you want to see a bit of the world on the way there or back. Singapore is worth visiting. I love HK but DH hates it but as Cathy Pacific was the best flight deal we haven’t stopped over this time.
I do my homework but then go to Trailfinders to book. If you also book a hotel with them, or another company,( even just one night) you get extra protection if anything goes wrong.
They were fantastic when we got stuck in Perth when Covid struck.