Priority passport renewal as dual citizen

[LaurelGrove]

Hi - has anyone used the one week premium renewal service recently as a dual national? Not the one day one where they give you your passport on the spot (digital premium service) which can't be used if you are a dual national, but the one where they promise to send it within a week (fast track).
First question: what is the turn around time, in reality? And second, do they take any existing passports (UK or otherwise) from you and then return them? I need to renew my UK one but can't be without my German one as I need it for travel next month, so can't risk not having it back in time.

Our baby is entitled to dual nationality and it never came up during the one week fast track appointment. We just provided all of her documents and we got the passport less than a week later. That's for a baby though.

I had an appointment on Mon 15th Aug at 4.15 for adult renewal
( 10yr issue date issue!) Flying Sunday hopefully! Do we think I'll get it through on time? I feel fairly hopeful. Might ring and check tomorrow. Has anyone else done this this month? Also just thought is the secure post included in the fee as I didn't tick that box. So stressful this passport stuff!!!