Worst experience with a car hire company

Chose this company as the price was competitive.
Website not user friendly.
Having paid a deposit, balance converted to euros at a poor rate increasing the overal price.
Requested confirmation of fuel policy – took two weeks to reply and gave incorrect information (as I subsequently discovered).
Tried to cancel but unable to do it on their website.
Printed voucher to find hire times had changed by 2 hours; 30 minutes later on collection and 1.30hr earlier on drop off.
Frantic e mails on day prior to departure led to a replacement equally wrong and eventually a correct timing and original price.
On arrival, Sixt wanted to charge me an extra day (50 euros) for the “change”. Fortunately, having been delayed over an hour on the flight, Sixt agreed to honour the original price and entered details manually.
FastCarhire hid behind voicemail, whcih they didn't respont to and e mail which can take an unknown amount of time. Without telephone contact in case of queries/emergencies it is not effective.