Modify UoBLab.cls font letter

Posting this as an answer, since it worked for you:

You want to use TeX Gyre Heros, the clone of Helvetica that ships with TeX. In PDFTeX, the code for this is,

usepackage{tgheros}
renewcommand*familydefault{sfdefault}
usepackage[T1]{fontenc}

If your document uses fontspec, you instead want:

setmainfont{TeX Gyre Heros}
setsansfont{TeX Gyre Heros}