ok . problem solved
last weekend i took a piece of carpet with rubber backing ( left over at work ) & cut it to the lower part of boot floor .
then i sprayed the rubber underside of carpet with BBQ black spray paint ( 2 coats) & once dried slipped it into place with rubber side up obviously .
today on usual friday jaunt for goodies & no slippage from anything
a simple thing i would say for BMW to have the well cover reversible with a non slip side ? 8)