UK customs have a new procedure for clients importing household effects under transfer of residence. The customs form C3 no longer applies.
 
Clients must make an application to HMRC using the online form, link below.
 
They must complete the form and upload supporting documents.
 
Each client will then be give a unique code to allow them customs clearance.
 
https://www.gov.uk/government/publications/application-for-transfer-of-residence-tor-relief-tor01

you need to prepare and scan below documents in your computer before you start to fill in the online form
1. passport copy
2. Hong Kong address proof (utility bill of six months old)
3. items list (put your name and sign)
4. UK address proof