Hello all.
Thanks for your answers. This is what I intend to do _in the first instance_: Wash the pan thoroughly in hot water only. Dry thoroughly with some kitchen towel. Put in enough oil to cover the bottom. Heat to a reasonably high heat. Drain. Wipe with some kitchen towel, while still hot.
P.S. I didn't return the pan to Sainsbury as I didn't believe that it was actually faulty; but I was disappointed with its performance (or lack of it). P.P.S. I don't do enough frying to warrant getting a cast iron one.
A Happy Christmas to you all.
Sylvain.