Authorization to get married to a foreign national in the UK?

I am a British citizen and my girlfriend is Taiwanese, we plan on getting married next summer (2011) and need to know what the process is. She lives in Taiwan and does not have a resident visa for the UK. Taiwanese citizens can stay in the UK up to 6 months under the visa waiver programme, does she still need authorisation to get married in the UK? How long can the process take? Can we apply for authorisation when she is here, or does she have to apply from Taiwan?