becky - it does sound like he is showing signs of being ready.. as i said in a previous post i used to work in childcare before i had my bub and i did alot of tt because i worked with 2-3 yr olds... 22mths is not to early to start if he has some understanding eg you can explain to him big boys go to the toilet, or if you have alot of time and you can watch him for the signs that he needs to go and stick him in the toilet.. before you learn these signs you may just have to stick him on the toilet every 1/2 an hour till you get some success and are able to praise him... if your not sure though and dnt knw if he is quite ready or if you have the time to focus on it so much now id suggest you wait becuase starting toilet training and then going back to nappies can tend to set children back and they will tt much later in many cases because they get confused..
hth feel free to ask any questions