They drive you to an office block miles from the airport in some seedy little office.
They damage your credit card in so that it is unusable then try to get you to buy their comprehensive insurance and if you refuse they call you a "no show" and keep your deposit. They have a "clean out clean back" policy which isn't mentioned anywhere which means you must have the car valet serviced or pay another £20 and they charge you £5 to take you BACK to the airport drop off zone.
Then just ignore your emails
And stay clear of CARJET who are just intermediaries and it is not possible to contact them post event...