Hi we are a couple flying from NZ to London in June with touring bikes and equipment. We need a place to leave the boxes until our return a month later. Any suggestions?

I live in Leeds, not London, but it will be much easier for others to help if you state which of London's airports you are using?
If you can't find any assistance from a bike shop and you won't be spending a night in a hotel that you could ask, you may have to go with throw-away cardboard boxes, but then you'd need help from a bike shop to get more boxes when returning to the airport ?? I'm no expert here, but may be doing the same type bike tour in a few years. I will consider buying a used bike once I arrive, especially if the person or shop would buy it back at trips end.