I think the ones who flout the rules, only see themselves as individuals. 'It doesn't matter if we visit. What difference does one visit make? And we won't go anywhere else'
They do not realise that they are not just one household, but, unfortunately, one of thousands of families, all thinking like that - and that is where the danger lies.
As vegansrock says, visiting ad keeping a distance is within the rules. My DGC visited their other Grandma yesterday. They stood at the road end of the front garden, about 10 metres from the house and unfurled a banner saying 'Happy Easter Grandma'. Grandma stood at the front door. There was a brief conversation and they went home. No contact was made and not even any parcels shared.