Carjet are a basically a good company to go through although there are odd quirks.  My son recently had a car from them and the amount you pay when booking covers all insurance claims, there is no excess to pay when you pick up the car from Solmar.  Also petrol has to be paid for at the time of renting but the charges are not the excessive amounts you would have to pay if you returned the car with an empty fuel tank to any of the other companies.  Also a guest at our property ordered a car from them and when he went to pick it up he had been upgraded to a better model and got a brand new car into the bargain.

The only problems with Carjet are, as my son found out, that they only take credit card bookings and as he refuses to hold a credit card, guess who had to produce theirs.  I believe that you can pay cash at the time of pick up but they don't take debit cards. And although he received a quote which was supposed to be valid for upto 3 days, when I came to pay the quote had risen ( about £1-50), even though it was only the following day.
When my son queried it with them they told him that it is normal for quotes to rise and would not give a refund.