Thanks for all your contributions - Got a result !!
When the girl at the Car Rental Desk asked for my Credit Card , I handed her my Debit Card .
Straightaway she said , "this is a Debit not a Credit Card" .
I just calmly said it does both .
She hesitated for a second or two , then went ahead...
I am greatly encouraged by both of your answers .
So , on collection of the car, I can take up the option of the paying extra premium to cover the excess .
I'm more than happy to cop that - it's totally my fault .
Thanks very much for your help .