Vodafone warranty - when does it start?

My HTC Desire's sound from the speaker has stopped working. Works Ok through headphones and even reverting to an nandroid backup from months ago has not recovered the speaker sound, so I'm pretty certain it's a hardware fault.

Problem is I am not sure if I am still under warranty. I have a 24 month Vodafone warranty but I ordered my phone on 10th Aug 2010. However I didn't receive it until 3 weeks later as it was out of stock - surely the warranty should only kick in from 31 August?

I haven't phoned them yet...