The online companies who offer it let you choose it as a delivery option, then usually charge a fee (although it appears free to both parties). An online company who don't offer it have agreed to let me order using it. Is it as simple as addressing my package to 'My Name c/o Post Office Local Collect' followed by the full address of the Post Office?
Or does anything else need to be in place, e.g. registration of the online company with Royal Mail? I ask because RM's online help says:
Which implies RM or the Post Office have been given my details by the sender. What would this helpful online company need to do first?'We’ll send your customer an SMS and/or email when their parcel is ready to be collected from their chosen branch.'