London 2: What time is everyone arriving?

Sunshinejar

So we are travelling up from Cardiff to watch the show and will be getting to our hotel at around midday, I know ticket pick up is from 2 but we were hoping to go and see a little bit of London before we arrived. For those who went to London 1 do you think arriving at 5 to pick up tickets and queue for early entry is pushing it? 

Advise welcome with timings! Thanks guys!