L&B, we found one gro bag in size 0-6 was enough - we bought 2.5 tog, which has suited all three of my kids (Feb, Jul and Oct babies) because we swaddled until they were about four months and then put them into the gro bag. So we only used the 0-6mth size for a couple of weeks or maybe 2mths at the most.

If its a good sale, the bigger ones would be a good buy. I've got five size 18-36mths - two 1.0 tog, two 2.5 tog and one 0.5 tog. Have rarely used the 0.5, but definitely need the others. One to use, one in the wash type scenario.