Couldn't agree more, heading down there tonight after work and not leaving without a refund.
Sounds like Argos are the problem not Fitbit. Argos are in breach of consumer law if goods not lasting long enough and suspect some persistence in advising them of their contractual obligations would have yielded better results (ie they are trying it on with less clued up consumers and need a slap)!
I also had an issue with the software. It was double counting steps. So they sent me a replacement. Same issue. Turns out, it was syncing it's own steps and those from Strava so double counting. I removed Strava. Told Fitbit, and they said keep it. They also replaced the wifes Alta when it had a weird glitch that auto corrected.
Read a good review of the FitBit Charge 3 yesterday here.
I have always loved FitBit, but I am now holding off to see what the new iWatch may bring.