Best of luck getting that job Kate.
With that great attitude of yours you are already a winner
I also have a bit of what sounds like a lisp and problems with the S sounds which seem to be worse when on the phone, tired and just feeling plain lazy to try a little harder.
Over the phone I have been accused of eating and also having a bit of a tipple so face to face would be easier for me too.
Best wishes for getting this job on your merits which is all it should be based on.
Gabriele