Phone up UK CAA FCL, the people answering the phones, will steer you in the right direction.
Yes, Initial Class 1 (quite a queue).
If you are "Current" on a type, you can transfer that to the UK CAA ATPL, with a skills test. If its a lapsed/Parked rating, you have to approach an approved ATO.
You may need an English language test.
You would need to let the HK CAA, verify your ratings.
Some paperwork, is a pain, getting people to certify your passport, licence etc. Get that sorted before you leave HKG.
EGGW