isn't he a little too young for knickers?

I dont think so... i put C in knickers from about 14 months i think?? Mainly to get alittle air not so much training till she was about 17 months... and also the cost of nappies was getting alittle crazy!!

Pull ups are pretty expensive compared to nappies & they really are too much like nappies... Maybe use them for nap time during the day & trips to the shops when it might be hard to run to the toilets.  Be sure to make it clear that he can pull them up & down to go to the potty. 

Buy 20 odd pairs of undies, they're cheap as chips & they are so little, they are easy to clean & change when they have an accident.  Let him pick the ones you buy so that he feels some pride & ownership; he'll be more likely to want to keep them clean.

I agree totally...go the undies!!! Pull ups are great for when you are on the go and can't always get to the loo in time! Shopping, longish car trips, night time etc.... However as they feel like a nappy, they get treated like one. Also, they are not too bad to get down, but can be  tricky for them to get back on! The look on their face when they realise undies are NOT like nappies is priceless! It is great as they start realising when  they need to go for a wee quite quickly! ( That is if they are ready ...your son definitely sounds like he is at that point!) When I popped my daughter in undies at about 20 months, she would race outside on the lawn for a wee as we only had one loo and it was up 22 stairs...not good when you have to go NOW!!! Number two's took a bit longer, but had to insist they were done on the loo!! She refused point blank to ever use a potty!!!! Hence the lawn for wees until she could understand properly the sequence of full bladder, need to go and I need to say so sooner rather than later!!! When a poo was on its way I would grab her and race up the stairs to the loo. She LOVED her undies. She picked them out and thought she was SOOO grown up wearing them. I had to stop her showing them off to everyone!!!!