UPDATE: Hi everyone. Thanks to everyone who responded and advised me. I had the telephone consultation with my GP today. I have now had the decision to replace my injections with oral medication reversed.
This is the gist of how the consultation went (excuse any lack of knowledge/understanding at times): I said what I had been told by the nurse at my last injection "that only those with diagnosed PA would receive lifelong injections from now on" and she said "yes, that's right"? I asked why I had originally been diagnosed with PA and now this is no longer the case. My GP explained that although she had given me literature on PA at the time of B12 deficiency diagnosis, this was just to highlight the signs and symptoms of PA. However, my intrinsic factor test was negative. ?? It appears then that those with negative on this test at my surgery will be switched to oral from now on.
I said how my initial symptoms of numbness in legs when standing/unsteadiness etc, which increased in frequency to around 8 times a day had responded well to the injections initially. However, they always return around 7-8 weeks after an injection - albeit, not as frequent as before receiving injections. I had previously discussed this with her and as a result she referred me to a neurologist. I quoted the neurologists report confirming severe symptoms due to prolonged deficiency of B12. I also quoted he was happy to see me again should the symptoms not clear up totally and he would conduct further investigations/scans. I said I was very concerned that oral medication doses would not be high enough to treat or sufficient enough due to me continuing to have the return of neurological symptoms prior to my next injection.
I quoted the UK guidelines stating that the only recommended treatment for those with neurological symptoms is via B12 injections. I said I had read how under-treated B12 deficiency can result in potentially irreversible neurological damage - sub acute degeneration of the spinal cord. I quoted the BNF prescribing guidelines stating that those with neurological symptoms should receive a maintenance dose of B12 every eight weeks - not 12. She said she hadn't heard of the eight week prescribing and had always prescribed on a 12 week basis. (Hopefully she will now go and have a look for herself). However, I plan on visiting her in the next few days on a different matter and I will bring a print out of that then to show her.
Since all of your help and advice on here I decided to look into other causes of B12 deficiency, I came across information on how previous stomach surgery can result in malabsorption issues. As I myself had bowel surgery twice a long time ago, I informed her of this. She wasn't aware of it, (although it's in my notes) and immediately said that as a result, I could continue on the injections as this is most probably the reason for the long-term deficiency.
Next steps:
Before my next (12 weekly) injection is due she will check B12 levels to look for signs of any trough and to determine whether more frequent injections should be given. She will also check: folate; intrinsic factor and celiac. She said that should these all appear okay, she will refer me back to the neurologist for further investigations/scans.
I understand this is not over for me as I know I need more regular doses and may well resort to self injecting, however, I am relieved of my biggest worry - that my symptoms will return in full force. Again thank you everyone who helped with this.
Gp review after b12 stopped 
GP stopped B12 injections 
GP stopped B12 injections
GP stopped my B12 injections after nearly 40 years
