a) What the database is (the spine, SCR, or whatever are all mumbo jumbo to me)
The NHS Database (aka the "Spine" or "NCRS" or "National Care Record Service") is exactly that - a cental DoH-controlled database aiming to house the entire nation's medical records, both a summary (the "Summary Care Record" or SCR) and also the entire GP & Hospital records (the "Detailed Care Record" or DCR).
b) What data is going into the various bits
c) When our data is being (or has been, or will be?) entered
The "true" Detailed Care Record (that is, a joint hospital & GP record) isn't available yet, though in parts of esp North & East England the GP records are hosted on central servers and made available community-wide (I'm not sure of hospitals can see the data). See http://www.ehiprimarycare.com/comment_and_analysis/383/making_a_detailed_care_record_a_reality
The Summary Care Record - consisting initially of basic information such as main diagnoses, allergies, medication - is live in 6 "early adopter" PCTs, and shortly in a few more. About 200,000 summary care records have been created, but in those PCTs not all GP surgeries are participating (yet). The SCR is already being "enriched" with more and more data from GP records, even before nationwide rollout, becoming a "detailed" Summary Care Record.
d) Who is entering the data
e) What we have to do about it and when in order to stop the process
If your SCR has already been created you're too late. Whilst if you ask for your data to be deleted (and the PCTs do not advertise this) then your "working" record will be erased but the NHS Database will store/archive a copy of your records indefinitely for "medicolegal puposes", even if your SCR has never ever been accessed, seen or used in a clinical situation.
Otherwise, your GP surgery may have stated that they will not create SCRs without your explicit consent (e.g. http://www.abingdonsurgery.com/viewmessage.aspx?messageid=30 or http://www.oaklands.info ). In that case, you may not feel the need to do anything. Opting out as below will however ensure that your GP surgery cannot be coerced or forced into uploading your data.
That leaves opting out itself, which you can do in a number of ways:
1) Fill in a form (e.g. from http://www.thebigoptout.org ) and hand it in to your GP surgery, post it, fax it or (if they'll let you) email it.
2) Verbally advise your surgery that you wish to opt out. You do not need to make an appointment with your GP just to do this (they won't be impressed) but the next time that you do see your GP just ask to opt out. You could state your wish at reception (but they might not know what to do) or over the phone to your GP (if you're ringing him/her about something else) or by email to your GP (if he/she allows this).
You do not need to opt out in person if you don't want to. You do not need to give any reasons or justification for opting out. You do not need to "discuss the issue" with anyone.
Opting out simply means the addition of the read code "93C3" to your GP record, which will prevent any uploads to the Spine.
Opting out of the DCR remains uncertain as yet.
See http://www.nhsdatabase.info or http://www.thebigoptout.org for more info