Thanks. It was DW asking. She's taking a trip to the States in June and will be wanting to rent a car. Normally I do it on my card. She tried to get a credit card last year but was turned down.
Tykeman, has D gotten a catalogue line of credit at all? That's usually the easiest thing to come by - as a starting point. I just placed an order or two with Simply Be, for example, and voilà, I had a line of credit in two shakes.
We changed to banking with Nationwide & DH got a credit card (his first ever!) pretty easily there. I am an authorised user on it - however, credit card accounts in the UK are sole name only, in terms of who is responsible for paying it. So being an authorised user isn't something that is going to go on the authorised user's credit file - it only goes on the person's who is solely responsible for paying the bill.
Also, getting a mobile contract plan is another way to build credit, if you've not explored that.
There are also the 'high rate' 'high risk lenders' out there, such as Vanquis - worth a try as a last resort perhaps.
We have rented a car (in the US) in the past using our visa debit card though.