If the addresses had two blank lines between them, you could do a search and
replace for two paragraph returns (^p), and replace that with a temporary
character, e.g. *.
Then do a second search and replace, and replace your paragraphs/line breaks
at each line of the address with a comma and a space.
Third search and replace would put back the lines between the addresses,
replacing the temporary * character with a paragraph again.

This would give you one line for each address, and then you could sort the
lines alphabetically.

I know it sounds long winded, but sometimes you have to think round corners
to get search and replace to do what you want!
Genine

Hi Stuart,

Still another method would be to convert the text into a four-colum table
(or five columns if there are empty paragraphs between records).

Then you can sort the table, using any column as the sort key, and later
convert back to text (Table > Convert...).

Regards,
Klaus