I am a British expat living in Riyadh, and wish to visit china for holidays at the end of April.

Please apply for China visa in early March, a single entry China visa is only valid for 3 months, if you apply it too early, it expires when you go to China, if you apply it too late, teh time is so pressing that you can't obtain a China visa on time, it takes 4 working days for visa processing.

Please contact the below two offices to submit visa application, China embassy in Riyadh doesn't accept application from ordinary passport holders:
Chinese Competitive Spirit Co. for Visa Service
Address: Olaya District, 62nd Street, Sada 1 Business Center, Riyadh
Tel: +966-1-4621258,0501086100
Fax: +966-1-4633850
Office Hours: 08:30-14:00, Saturday-Thursday

Alsandross International Est.
Address: Bin Salem Trading Center, Takhsossi Street, Riyadh (next to the Emirates Airlines Office)
Tel: +966-1-0535363247
Office Hours:
08:30-13:30, 17:00-21:00, Saturday to Wednesday;
08:30-13:30, Thursday