DS is a big wetter and sleeps for 12 hours at night so we use a Huggies nappy then a Huggies pull up in a large size ( I think they are the 14kgs+ ones) over the top. Because the pull up is big it pulls right up over the normal one and then any leaks get caught by the pull up. Some nights the pull up is dry and we can re use it!
Give the Coles brand ones in the green packet a go (they have a gumnut design on them). It's completely escaped my mind what they are called, dry something...I forget. Anywho I found them to be really good, DS is a really heavy wetter and a tummy sleep too, they last the night. Very full in the morning but no leaks. They seem to have quite a bit of padding, thicker to touch than Huggies.
Thanks ladies! - i'll be trying both these suggestions as im at a loss what else to do