The development of accurate techno-economic models is crucial to boost the commercialisation of floating offshore wind farms. However, conventional techno-economic models oversimplify operation and maintenance (O&M) aspects, neglecting key maintenance factors, such as component failure rates, metocean conditions, repair times, maintenance vessels and ports. To address this limitation, this paper presents an O&M-aware techno-economic model that comprehensively incorporates the most relevant maintenance factors and evaluates their impacts on site-identification across the North Sea and the Iberian Peninsula based on diverse O&M strategies. Results reveal that operational expenditure can contribute significantly to the levelised cost of energy, ranging from 22% to 50% in the North Sea and 19% to 46% in the Iberian Peninsula. Furthermore, results demonstrate that suitable sites vary based on O&M strategy: preventive strategies favour areas with abundant wind resources like northern Scotland, Norway and Galicia, whereas corrective strategy prioritise sites with less severe metocean conditions, such as southern Scotland and extensive regions in the Mediterranean Sea, including the Gulf of Roses and the Alboran Sea. Finally, the downtime of turbines, an aspect traditionally neglected in techno economic frameworks, emerges as a key factor for accurate techno-economic assessment and site-identification.