This company claims to send emails to customers, but I didn't receive any, so I couldn't find the contact information for the pickup.

Most car rental companies operate similarly, just follow QEEQ's guidance to avoid any pitfalls.

The final rental was not Nissan.

It did not exceed my expectations as I booked an estate vehicle but the car I received was a cross over SUV which has a small/medium boot but I needed a large boot. I was told they accepted American Express for the deposit which they didn’t accept on arrival and I paid an additional £165 on top of the rental agreement to cover the fact that they told me they do not accept Amex upon arrival

Not bad, the store owner recommended insurance, but they didn't push it when I declined.