What do you mean by the sim card being "Flaky"?
I have a spare phone (an old nokia) with a giffgaff sim in it. It started messing about and not making calls, although it would receive ok. It worked fine for both in an Ericsson phone. I did a sim swap and it worked fine.
I would definitely recommend doing a sim-swap and/or trying your existing sim in a different phone.
Your right I could, but I don't want to, Thanks for your valued contribution to my dilemma, should all else fail your suggestion will no doubt be the winning post