Mercey, first selected for England U19 duty a year ahead of many of his peers, was again called up for England U19 duty in the 2006 World Championships.
Mercey was first selected for England U19 duty a year ahead of many of his peers, which included four appearances in the 2005 IRB Under 19 World Championships as well as outings in the 200405 U19 Six Nations. Mercey was again called up for England U19 duty in the 2006 World Championships, before once again taking a step up ahead of his peers to represent the Under 21 side at the 2006 IRB Under 21 World Championships featuring in winning sides against Fiji and Wales. 
