A colleague (who is currently submitting a theory that may well win Nobel Prize in Physics)has solved issue.

Where you set the conditions you also select which products it applies to. I assumed, stupidly, that not selecting anything, the cart would just "know" how many items there were and apply the appropriate shipping.

No, incorrect assumption.

Where you set the shipping, you must select which products the condition applies to, in this case "All Products".

Once this was done to all for conditions, hey presto, it works.

cheers to all

Craig R.