This isn't a UK bill. This is a pardon in the form of letters patent coming from the Queen. The form, "To all whom these Presents come, Greetings!" is pretty common in letters patent. There may not be a normal court in Sandringham, but this isn't coming from a normal court. It's coming from the Royal Court, which takes on the name of wherever the Sovereign is in residence. In this, the Queen is staying at Sandringham, so that's where the Royal Court is.
