Excellent - You can't use a Prepaid CC to hire a car.
Square one! 
From the Cash Plus Q&A
"Are there any restrictions on where I can use my card?
Just a couple, so if you want to:
Buy petrol or diesel at a Pay at Pump, we’ll need to switch this service on. Please contact our Customer Services team, so that we can review your account.
Hire a car in the UK or abroad, we’ll need to switch this service on. Please contact our Customer Services team, so that we can review your account."
So, yes you can, but you will need a minimum amount on your card that they will reserve, so it will be money tied up until the hire period ends plus the time period for any potential cost of speeding fines etc.
For damage waver excess I have used UK companies for this as it was much much cheaper, 'Google' hire car excess insurance. This will pay out on any excesses you have to pay. Not that I've ever had to pay an excess, despite the slight valence and sump scratches where I was talking to the Mrs and missed the two narrow track bridge beams across a ditch,

not to mention the sump on the centre sections of village dirt tracks.
