Children's clothing sizes vary greatly by country. To give you slightly better idea of what size would fit the best please, use this sizing conversion chart.
|United Kingdom||European Union|
|3-4 years||98-104 cm|
|4-5 years||104-110 cm|
|5-6 years||110-116 cm|
|6-7 years||116-122 cm|
|7-8 years||122-128 cm|
|9-10 years||128-134 cm|
More info about returns and exchanges here.