Sixt complaint: service

This office location is an absolute disgrace. My email correspondence showed location on International way. I arrived to find it closed with a note saying staff will be in Car Park B Level P2, with no directions how to get there or where it was. After finding westfield security staff, they pointed me in the direction of the car park, once there still no idea where the Sixt office was no signage nothing, after speaking to members of the public I was directed to the next floor up and again once there no signage. Once again I found someone to ask who directed me to the very back of the car park. I entered the office complained about no directions and got a comment back of well you made it now Because I was six minutes early I was asked to wait outside in the carpark and not even invited to sit and wait inside, appalling. The Staff member stated they would upgrade me free of charge, after getting the car I couldnt really check for damage as the car park is so dark, The car didnt have the usually USB charger , so I couldnt charge my phone I went back and asked for another car , they said they didnt have any, so what happened to my original small car ? it wasnt a free upgrade after all. After driving away and on the motorway alarm went off engine will shut down after 90 mile unless I add adblue what! I called customer service to find it was for deisel cars, I wasnt even told it was a deisel and it would cost only a few pounds to fill up and the company will reimburse you. Unbelievable!! I managed to find a service station that sold it and it cost £15. Absolute disgrace, this should have been done before handing it to a customer. I will never use again or recommend. I feel sorry for foreign nationals who hire a vehicle from this location.