I've been inside the national parts centre in Leicester - we are one of their suppliers for pipe fittings etc. Impressive or what!!they have their own parts distrubtion net work for next day dilvery from post office
They have over a million pounds worth of spare parts just for their own semi-automated picking equipment in the centre in case anything breaks down so they can keep working.
Shed loads of blue boxes sent out to fitters daily via the post office.