Completely agree with Bex on pull ups. We took a week off and did naked bottom for a day and then added pants, then trousers over a few days. By the end of the week we realised he wasn't ready to do it full time because he couldn't warn us more than 30secs beforehand that he needed to go. That was when he was 21mths tho, so speech might have been a factor. We didnt abandon it all together though. We decided to stick with pants at home with nappies at naps and when we left the house. We gave it a couple more months of just encouraging him to go on the potty at home, before having him nappy free at my mums and then starting at nursery when he was 23mths. It really began to click over the summer, though he kep having accidents at nursery. For the last two months though he hasn't had an accident at nursery. Occasionally he has tiny drops in his pants where he's managed to stop himself, but I have him in pants all day now. Poos are more tricky because of his constipation issues but we allow him to ask for a nappy to do his business which has helped. For us training has been very slow but it worked 
