Hello yohan, I hope I don't come across as too pushy, but I'd like to point out to you a few points as I have done with other merchants in the past in regards to accepting bitcoins as payment.
The main point I'd like to make is that if you use a merchant service provider such as
http://bit-pay.com/ , they actually protect you against volatility and insulate you from that risk a few different ways. They allow you to set a price in GBP or USD or whatever currency, and then dynamically update the bitcoin price themselves.
Then, when someone decides to order, they lock in the price for 15 minutes to give the person time to pay, and guarantee you the exchange rate during that time so you won't lose out to fluctuations.
And once the customer has paid, they instantly convert to fiat money and deposit it into your bank account. With bit-pay (not sure about others), they also offer you the option of splitting the payout so you get some fiat and some bitcoins.
I hope this bit of information enables you to look into using a merchant service provider like bit-pay or paysius.com, and end rant thanks for listening.