I was told the main reason for centralisation was to avoid having loads of blank passports all over the world just asking to be stolen. Germany does the processing of the applications but the actual documents are issued from UK somewhere.
I applied for and got a second UK passport (not from UAE, from Qatar, but it's all the same nowadays). No hassle and it came back via courier in about 10 days. I was surprised at the speed - - but it's all a lot more expensive than it used to be.
