Our plans stated 330x100x150 deep concrete padstones to support our
152x89 Universal Beams. Total length of beam was around 6m but
supported around halfway along its length as well as at each end in our
case.

The sizes of the beams and the sizes of the padstones were calculated
by a strucural engineer based upon the plans drawn up by our designer.
It was a couple of years ago now but I seem to recall paying somewhere
around =A350 cash for the engineers report which had to be submitted
along with the plans to the BCO.

Suggestions I heard for the padstones were to cast them myself using
concrete or to use kerbstones which are also about the right size. In
the end I bought some concrete lintels and cut them in half.