I'm the same tallboy. I've no idea what my blood group is. My GP doesn't hold that info. Only if I'd been pregnant, given blood or needed blood, would I then know. Seems crazy to me.
Its a good thing to do too. Like Tony Hancock said, "Just like any other bank, you put it in when you're flush and draw it out when you need it!". I'm not allowed to give A+ blood anymore due to blood pressure pills, but I've got 52 pints in the bank!
I am group A+.
I only know that because of the plastic key ring that I keep with my house keys on another key ring. Its good to know what you are though, may come in handy one day.
I am not sure why one needs to know one's blood group as if blood is needed, the patient's blood is cross matched against the blood that is to be transfused.
If it is an EXTREME emergency, then O rh neg can be given whilst the cross matching is taking place.
You can do a simple test yourself. I had long ago been told what my group was, but had forgotten if it was A neg or B neg, so I bought one of these test-kits and it came up with the answer pretty straightforwardly. Click http://www.ebay.co.uk/itm/1-x-BLOOD-GROUP-TYPE-HOME-TEST-KIT-CE-MARKED-/220368905559
Mind you, I'm a diabetic and so used to taking daily blood samples, so - if you're squeamish - it might not be as easy for you. Over to you!