My advice is none of the above. Shop around for the highest interest rate savings account, and put the 150e a week in that. This will put you in the enviable position of having substantial savings put by to do with as you wish, pay a lump sum on your mortgage or pay cash for car.
Alternatively, you could use the savings in the CU to pay for the car, and start building your savings back up there if you wish to keep your savings in the CU, although they may not be paying as much interest as you are paying on your mortgage.