I read somewhere that all UK passports were renewed, in the Far East, by a company in Hong Kong and a courier service was needed to make the application. I understood this was the UK Govt plan for outsourcing... so they could eliminate the Civil Service Union 'jobs for life'.
My info may be out of date but worth a search.
EDIT. My info above IS out of date as from last 3 June 2014 (my birthday)...
Passport renewal delays causing expat headaches - Telegraph
It appears ALL renewals are done in UK and can take up to 6 weeks...I also found that UK passports (EU) can be extended for 1 year...didn't know that. Mine has never been used and is 5 years out of date. I'll wait till UK leaves EU coz they will then need to issue another passport.