"To be supplied at the rate of£100 per m 3 plus a£450 delivery charge"
". . . a 'construction contract' means an agreement with a person for any of the following . . ." and subparagraph (a) is "the carrying out of construction operations". "
"manufacture or delivery to site of— (i) building or engineering components or equipment, (ii) materials, plant or machinery, . . . except under a contract which also provides for their installation."