Boxing a bike at Heathrow

Hello

 I will be on a self supported bike tour of England and France .At the end of my tour I will be staying at a hostel in London and I plan on biking to the airport and I need to find the preferred method of getting a bike box delivered to Heathrow so that I can box my bike before departure. If there is a better way to get me, my bike and gear, and a bike box to Heathrow please advise.

     Thank you

       Robert