IT & NHS will never work.
I moved house in march 2002, and told my GP. In september 2003 my optician wrote to my GP recommending I be sent to a consultant regarding a change in my field vision. My GP wrote. Nothing was heard. I chased it, GP wrote again. Nothing.
After a year, we received a handwritten note from the hospital saying they had a letter returned from the address they were sending the booking to, and was this address my new one. A visit to the GP confirmed that the GP had correctly passed my address on, but the muppets at the hospital were using one they held previously.
Saw consultant. Diagnosed with glaucoma (so a years delay was a great help). Mysteriously, all his letters never arrived too. Asked him to check the address was right - he looked in file, and there it was clearly printed correctly. All was well.
Still not receiving any letters. Checked again. He actually phoned his secretary in front of me, and they confirmed the correct address.
Still no letters.
Finally, I was being seem by another specialist, and was asked to take my file from one clinic to another. I opened it up and what did I see. A sheet of 24 pre-printed address labels, with the OLD ADDRESS. I took them out, tore them up, and started receiving letters.
In any system I've built, I only try and store data once, and then reference it. Because I know what can happen if you try and store an address, phone number etc, in different places.....