I am boring on such things; all of my B&W products were either bought in a specialist store which is an authorised dealer, or, in a specialist airport shop, where - due to frequent travelling, (and a lot of buying), I knew the staff.
Thus, all were face to face purchases.
My suggestion would be that you phone them, (and soon; this is because an original purchase date of 'last November' suggests to me an expiry date for a one-year warranty might be rapidly approaching), explain (politely) what (you think) the issue is, and ask for suggestions as to how you might go about remedying it.
They might be able to tell you who to phone, or email, or send the suffering headphones to in order to get them repaired. If it is still within warranty (have you a receipt, a date, or an email which announces that something has been dispatched which might give proof of an exact date), this might come without charge.
If not, offer to pay, but suggest politely that - as it is so close to the expiry of the initial annual warranty - they might consider (as a possible gesture of goodwill) absorbing the cost of the repair (and perhaps postage) themselves. Sometimes, if you are polite and respectful (as opposed to demanding, aggressive and sounding as though you are entitled), this might work. If they offer to take them, and you are close to - or can travel conveniently to - where they can be collected, I suggest that you drop them in personally.
Good luck. I know what it feels like to lack one's P5s
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