Acquiring a Chinese Visa from Hong Kong is quite easy. Chinese Visa Services are everywhere in HongKong, and prices range is from 300 HKD to 1000 HKD depending on the speed of processing.

The best and cheapest place to get Chinese Visa is the Chinese Embassy in Wanchai, Hongkong Island.

Address:
Visa Office of People’s Republic of China,
Office of the Commissioner of the Minister of Foreign Affairs
6-7/F, Lower Block, China Resourced Building,
26 Harbour Road, Wanchai Hongkong
Tel: 3413 2300 / 3413 2424
Opening Hours: Mon-Fri: 9:00am-12:00nn; 2:00pm-5:00pm, Sat, Sun & Holidays: Closed

Getting there:
Take the MTR train to Wan Chai Station, Exit at the HK Exhibition Center exit, and walk down the overpass. Get down on the stairs to your right before the entrance (via overpass) leading to the Exhibition Center Building. Follow the road and cross a small curved road. You will then see an entrance (side of the building) with an officer in tuxedo. That should be it! You wont miss it as it always has a long cue of tourists waiting to get in the building.

What to bring:
1 Passport-size picture (with white background)
Ballpen
Passport

Fees:

Individual Visas:
Single Visa - HK $150
Double Visa - HK $220
Multiple Entry (6 months validity) - HK$400
Multiple Entry (12-24 months validity) - HK$600

Additional charge for special services (Individual Visas)
Express Service - HK $150 per person
Visa to be retrieved on 2-3 working days from application date.
Special Express Service - HK $250 per person
Visa to be retrieved on the same day of application date.

However, charges in the embassy do vary, depending on your citizenship, nevertheless, the embassy still offers the lowest and official prices for acquiring a chinese visa anywhere else in Hongkong.

A double entry visa for residents of UK costs 438 HKD