Streamline UK passport renewal so that citizens always have a passport

Presently, when renewing UK passports, you have to submit your old passport. This means you can have weeks but sometimes months without a passport. For those with travel booked, or for those with family or friends abroad, this can be a big problem. You can pay for a faster service, but once you've made the standard application you can't transfer. UK should adopt the Australian model, where citizens can carry on using their old passport until the new one is issued, allowing for seamless use.