[maffydub]

I would say "three July twenty fifteen".

It took me a while to figure this out because actually it's quite rare to speak a date including a year without reading it - most spontaneously-spoken dates are this year (so the year is implied) and for a read dates, I'd probably say whatever was written.

The clincher was how I'd say my birth date, which would be of the form above.

I'm not claiming to be the definitive British English speaker, though! ;)

...and as another poster commented, it might depend on context - for example, "September 11" is often used in British English because it refers to an American event.

[al45tair]

As a Brit, IMO both are perfectly acceptable in English prose. It isn't unusual to say "October the 4th" as opposed to "the 4th of October".