Hi, anyone got any idea what could be contributing to file size, if it's not
'extra' or 'hidden' data, and my file has no pivots, graphs or links outside
of the workbook?

I've even tried to copy the data into a new workbook, and rename all name
lists and so on from scratch - the file is still 21MB. It's only 4 tabs,
with 1 tab being a 'reference tab' for formulas, one other source file, and
two main tabs - one being only 150 lines, and another being about 8K lines of
data with formulae.
Is it the name lists? I have them assigned to whole columns i.e. V:V rather
than just the cells with data in it i.e. V1:V149.

I did see below link - no luck...
http://www.contextures.on.ca/xlfaqApp.html#Unused