OK, 2 updates.
1. Since Monday the phone, partnered with its giffgaff sim card, is now semi-functional: it is able to call out to mobiles, and receive calls from mobiles (at least some mobiles, others it refuses to connect to), and I can txt to/from some mobiles (again txting to some other mobiles, the same ones that calls dont work to, doesnt work). I probably have Shaun McGrory of giffgaff to thanks for this useful change to semi-operational status. Thank you Shaun. But, alas, currently still working towards getting internet access , and vmail access service via the giffgaff sim.
2. Ive now done at least a part of what people in the community have told me to do. In that I went down to carphonewarehouse and asked them to show me a sim card working in my nexus one phone. The chap put his own O2 card in and it worked: i saw calls working, txts working, and internet access working. He set nothing up - no configuration settings - just sim in, power on and go. I didnt check vmail. The chap did say getting a sim-only deal from O2 or others on a nexus one would not bring with it handset support, that would all be at my risk, but that said, the functions seemed to work out fo teh box, unlike with the giffgaff sim.
Suggested test done. Test results communicated to the community. I will also communicate these results to the giffgaff people via the facility they provide
So now I guess I could conclude, as a result of this wee test, that i now have access to one route that produces what look like functionally acceptable outcomes albeit with no support and not fully tested, that i could choose to follow.
I could also choose to accept and live with a semi-functional giffgaff service.
But lets assume that I still want the giffgaff service to work properly and fully in the intended fashion.
So, having done the diagnostic that I was asked by community members to do, and assuming that any questions I now put to giffgaff will be answered in the same way as the majority of questions Ive already put to them (ie they'll endearingly refer me to the user community for answers and help), and assuming that no new solutions come out of giffgaff (indeed they havent set an expectation that any new solutions would come from them) my question now is, what now to get internet access and to deal with the voicemail issue and the partial success on calling and txts ...
Im in your hands