Reffell captained Wales to a 41-38 victory over Ireland at Donnybrook, scoring the opening try as his team bounced back from a second-round defeat by England to win an 11-try encounter.
Wales were 19-10 ahead at half-time and Reffell gave them the perfect start to the second period, touching down immediately after the restart following smart work from wing Joe Goodchild, the Tigers flanker arriving in support to race under the posts.
An Irish score in the closing five minutes provided a grandstand finish, though the Welsh were able to hold on for their second win of the Championship.
Fly-half Hardwick started his first match at Under-20s level after appearances as a replacements in England’s opening two wins, but his try and seven kicked points could not prevent a 24-17 defeat by Scotland at Myreside in Edinburgh.
A Hardwick penalty provided the opening points of the evening before Scotland claimed a try, but England responded was the fly-half scored in the corner after a break from Ollie Lawrence. He converted his own score before Tom Seabrook added England’s second try.
Hardwick’s Tigers colleague Jordan Olowofela started at full-back but was sin-binned early in the second half as Scotland tried to claw their way back into the game. After punishing England with a penalty, the Scots took a 19-17 lead with a penalty try when a maul was brought down near the line and then added a bonus-point try from an interception in the closing stages.
England head coach Steve Bates said: "It’s disappointing because we created a lot of opportunities and didn't finish enough in the first half. We had the wind at our backs and we didn't capitalise on it and didn't turn that territorial advantage into points.
"We made too many mistakes and forced the game a little bit more than we should have. For a lot of these guys, that would have been the first time they have been in that position but they will learn from that and the real test is to pick themselves up for France."