By Guy Taylor Mace, the construction firm contracted to deliver London’s HS2 Euston terminus, has announced a new chief executive alongside a raft of top-level changes. Mark Reynolds will step down from his position after more than a decade in the role, to be replaced by deputy chief Jason Millet in January. Reynolds will keep his position as Chairman as part of a change in company structure, with the role previously held by every Mace boss. The changes come alongside ahost of switch-ups in the HS2 contractor‘s divisional leadership. Mace is planning to appoint Davendra Dabasia and Andrew Jack…