Building a 9inch cavity wall off a 4inch steel beamrest

[Andrew WAllen]

I am building a front extension, floor space 3 square meters with a 8inch wall with a 4 inch cavity. I dug the foundations and come across a drain pipe with 4 inches of concrete on each side of the pipe. Building control told me to dig 4 concrete pads 1 meter deep and rest two steels 7x4 on each end and connect a steel down the middle and 300mm of wall and cavity will be built of the steel. He then told me to wrap the 4 inch steel in mesh 50mm all the way around and 50mm of concrete which will give me 300mm wide and about 400mm deep and the shutter it.do I need to put bricks in the web of the steel.
is there another way of doing this? Can I put something else on top of the steel to make 300 mm wide. The steel is two courses below the DPC but will be 4 courses from the ground level