I know I am practically just talking to myself now, but I have got a finished
product. I would like to know if there is a more compact way of doing it
though. To cater for multiple lines I have thrown a SUM into the party so
that it will look at the total travel hours and the total site hours for each
day, over multiple rows, without having to use a second cell.

In the 1x column I have
=SUM((D3-C3),(D4-C4),(D5-C5))+(IF(SUM((F3-E3),(F4-E4),(F5-E5))<=8,SUM((F3-E3),(F4-E4),(F5-E5)),8))

In the 1.5x column I have
=IF(SUM((F3-E3),(F4-E4),(F5-E5))8,SUM((F3-E3),(F4-E4),(F5-E5))-8,"")


This caters for 3 rows per day but may be increased to six.

Thoughts.....