I'd say that phone numbers, like addresses, should be written in the format of the country where they reside.
Periods (not middle dots) are used by a few countries, e.g. Belgium:
If it's a UK phone number,
(0123) 456-7890 seems to be the common format.
If it's a Japanese number, then
(012) 3456-7890 works (except for the "free dial" numbers, which use format of
If you're putting the number down on a business card which you may give out in different countries, then the most appropriate is probably the international format:
+81 12 3456 7890 or
+44 123 456 7890.