1. This is the full tracking of your parcel:
China Post Register Air Mail Tracking System
Parcel No.RH339257924CN tracking result
2016-08-30 19:39:59.0 Guangzhou Int'l Parcel Center received
2016-08-30 19:40:05.0 Guangzhou Int'l Parcel Center customs scan
2016-08-30 22:33:04.0 leaving Guangzhou Int'l Parcel Center ，next station 广商大宗
2016-08-31 21:45:44.0 Shanghai Transit Station export security scan
2016-08-31 22:38:51.0 Shanghai Transit Station export customs cleared
2016-09-02 22:56:00.0 arrive Shanghai Int'l Airport
2016-09-02 22:56:00.0 arrive Shanghai Int'l Airport
2016-09-03 00:15:12.0 leaving Shanghai Int'l Airport going to next airport/seaport
2016-09-04 13:12:00.0 Shanghai departure

2. When the parcel arrive in UK you will be able to follow it on Royal Mail Site. You might want to read this for UK:
http://track-chinapost.com/China_Post_Arrival_Time_Stat.php

3. So far I don't see any problem with your parcel, you just need to wait for it.

Hope this help.

1. The tracking is already showing that:
2016-09-04 13:12:00.0 Shanghai departure

2. The hold up is in UK, mail bag are arriving in the Inbound warehouse, then it's taken care by Royal Mail.

Hope this help.

1. I suspect the Mail bag with your parcel in it possibly has arrive in UK bound warehouse like possibly thousands of other parcels coming from the rest of the World to UK citizens.

2. Whenever the Royal Mail scan your parcel then you can be sure the parcel is in UK otherwise the parcel is in transit to UK.

Hope this help.