They are now telling me, that if the foods are lost before they collect I
have to pay, but they have never been delivered why should I pay ?

Have I gone "off on one" or am I right ?

No you are not right, the goods WERE delivered just not signed for. Do the
right thing and own up to Screwfix. I use them a lot and would like to keep
costs down, but acting like this we all pay more in the end!

John