Noxion's points upthread are obviously correct and I'm almost surprised that they're controversial.
Where would you draw the line between individual and collective action? Surely the presence of some kind of organised campaign (not necessarily formally organised, but organised somehow) is the very thing that makes it more than an individual choice? For what it's worth, I think veganism/vegetarianism are far more "organised" than not using scab tills, but I'd still think of them as being about individual choice too.
I mean, that's the whole point isn't it? If there was a USDAW campaign against them, I'd support it, and avoid using them if that's what the campaign demanded. Or even by the Solfed shop workers branch or something similar (not that there is one, afaik). But there isn't. That's a crucial point imo - in the absence of that campaign, it's a bit like saying that a scab is someone who goes to work, without paying too much attention to whether they're crossing a picket line or not.
Fwiw, I thought the ticket office campaign was pretty inspiring, and seems to be actually winning. Comparing the successful ticket office campaign to the entirely individualised discussion around self-checkout feels like night and day, although obviously rail and retail staff are starting off from very different points in terms of existing organisation. Might also be worth considering that the asks the RMT made of consumers around the ticket office campaign weren't particularly based around "don't use ticket machines or buy online".