I actually thought the whole LGW experience was completely slapdash.
They sent me the above email apparently telling me I needed a credit card and proofs of address which were apparently not necessary, they went on to add
Thank you for booking your car rental through SIXT.
In order to provide our customers with the highest level of customer service possible,
we would kindly ask you to reply to this email confirming your reservation and which terminal you will be arriving at to collect your vehicle, whether that be South or North. If you are able to provide your flight number we would kindly ask you to do this as we can keep a track of time and location.
This means that we can have the vehicle ready and waiting for you to get you on your way as quickly and efficiently as we can.
So I replied with my flight details but it turns out this is faux customer services theatre. They weren't "waiting for me." Having gone to the bother of checking the location information on the website, North Terminal office was closed when I arrived. There was a notice asking customers to call a number, which I did and there was no answer.
Here they are, the Sixt people at Gatwick not "waiting for me"
Rather than mismanage expectations upwards, ask customers for an action (the confirmation of flight details) so that Sixt can be nice and "ready and waiting" which they are not, plus introduce the necessity for additional proof of identity that we do not have, why don't they just shut up? not send any emails to us and let us work out ourselves which office they have bothered to staff?
By all means be a bit crappy, but why bother telling customers that you are going to right there serving up the finest customer service when you are not?
The agent that checked out my car was a complete gent, but perhaps someone needs to slap the management upside the head for sending out corporate bullcrap emails.