I'd expect the financial institutions to give you as much rope as you want (enough to hang yourself) especially as you have a guarantor. Will your guarantor be happy to sign again for a top-up? You say you have a bad credit record and have refinanced (at around 10%) which is fine but your looking for a top-up with only half of the repayments made. Have you factored in the tax, insurance, petrol, servicing etc.? You might be better advised to live without a car for a while longer but ramp up your repayments to pay off the refinance loan over 18 months or less (should be less than €800/month to pay off over 12 months). At that point you wont just feel you are back in control of your finances you will know so. Then buy a car for cash.