where to go from here?

We started potty training last week. I've started by having lo running around either bottomless, or just with pants on and he's really taken to using the potty. He's sat on the toilet a few times as well, but hasn't done anything in it yet. The problem is when he's wearing trousers - he's had a couple of accidents this week but I'm not sure if this is because he's been outside playing (hence being fully dressed) and distracted or if he doesn't realise that he still needs to use the potty when he's dressed. He didn't seem bothered that he was running around in wet clothes either. We have been using pullups but only for nap time, bedtime and when we're out and about as he's not confident at sitting on the toilet yet and I don't want to pressure him into trying to use the toilet when we're out.
I'm really happy with his progress, because he's generally a stubborn wee guy and resists change with all his force so I reckon he's doing well, but I'm not sure what the next step is?