Whether an individual’s L1 syntax is affected by the acquisition of an L2 in adulthood is under debate. Also debated are the drivers of language change at the community level. Under strict generative views (e.g. Lightfoot 1999), change is led by children when they receive input different from the previous generations. Under other views, the grammars of individuals can change across the lifespan. This paper addresses these issues by looking at the knowledge and use of sentence-initial non-nominative constructions by first-generation adult immigrants to the UK from Spanish-speaking countries. Judgement/preference task and production data indicate monolingual-divergent use regardless of intensity of contact with English, and monolingual-divergent syntax when level of contact with English is high (and Spanish continues to be spoken). However because in the UK neither first nor second generation Spanish-speaking immigrants live in ethnic communities, the second generation is less likely than their US counterparts to use the parental language beyond early childhood. This in turn suggests that any psycho-social variables involved in heritage language maintenance are not applicable in the UK. This leads to the prediction that despite indications of individual syntactic attrition by first generation speakers, because the second generation does not actively use Spanish, the emergence of new varieties at the community level will not occur in the UK.