Just so you don't all worry, plan B worked!
Being a genius, (a machine at a service station on the M1 told me I was genius when I was about 10 as I recall and who am I to argue?) I swapped the SIM card from the Mi-Fi to the dongle I bought last year. The software associated with dongle allows text messaging and so I was able to set up a new online account.
Simple really, but still a bit of a nuisance.
By the way, if you have a Mac and are running Snow Leopard, don't use a dongle. Ally tried it and it broke her computer. did something to the kernel and she needed a new hard drive as well as fresh installation of the operating system. The newer dongles might have fixed that, but the Mi-Fi seems a safer option because it doesn't require any software or drivers.