I wear an insulin pump and I guess I've been lucky so far, as I travel frequently to the UK and have so far avoided any whole body scanners. In the US, I've come across them a couple of times, notably SAN, and each time I've simply explained the situation and I was patted down pretty courteously and swabbed. If I do end up at a body scanner in the UK and am not given a choice, I will advise the person responsible that the pump has not been cleared for the device, that by European law they are obliged to offer an alternative method of screening and that if the pump is damaged as a result of the screening I would hold them responsible for it. I would then go through the scanner.