If I have a single cell with half a dozen phone numbers within it – how can I stack them in individual cells in a column?

Cheers as always

Select cell
Data>Text to columns
select "delimited"
select your delimiter (maybe a space?)
press finish
copy resultant series of cells
edit>paste special, transpose, OK

Cut and paste…

If it were more than 6 you could copy to notepad and import it into excel using spaces or ; etc to delimit the columns/rows (you may have to transpose…)