Like Italy did in their first wave? (didn't they? is that correct?)
My best guess is that in Italy, people who had no chance of benefiting were put on ventilators, but in UK, the realistic prospects were better assessed which meant 'the right thing to do was not to prolong suffering' by trying to put people on ventilators who couldn't benefit from mechanical ventilation.
It's just that if Italy & UK are about the same population size, but UK has had more actual deaths, and Italy had many more intensive care beds & ventilators, then it seems like UK should have run out of ventilators too. What am I missing? *
*I may be misinformed, glad to be corrected, if so!