Excel 2008 : Adding/Subtracting/etc money values that are split into £ and p columns

Attached is part of the sheet I'm working on.

All my £ values are in seperate columns - one for £, the other for p. I need to be able to calculate totals, and % of these totals, and subtract, all whilst keeping the column format. I've tried many ways of doing this with the MOD function, but I can only get a few bits to work (mainly the addition bits). I'm hoping my explanation on the sheet itself is clear enough as to what I'm after.
The % need to be reference to the % cells in Column E though, as these are not consistant numbers, and sometimes do not need to be included at all.

Many thanks in advance for any help