For a better grasp of the nature of new flexible migration, we propose a sector / country approach, given that employers’ needs for migrants vary by sectors (Caviedes, 2010) but are also shaped by different national actors (Watts, 2002). We select construction in Spain and the UK as the cases where the phenomenon is most visible. The comparison allows us to address, in sequence, the following questions: To what extent is migrant labour a buffer bearing the