"Work briefly anywhere there's a doinker, order a replacement doink-device, strip it down, walk around London bumping into people"
Do you really think you can work briefly in a shop and then order a replacement merchant terminal, set up an merchant services account, add on a private bank account ... etc etc?
You can't of course, getting that set up is not a trivial task. You may be able to set up a front organisation and set up a trade account but you are still going through quite big deal to be able to open a merchant account and accept contactless transactions all using fake IDs (you are asking for a merchant and bank account using fake details here!). However if you manage to get a fake account set up then you are better off just running an online scam, you'll get more money with less risk.