(Adds comments, updates prices) * Boris Johnson to meet European Commission president * Retail sales takes hit in November * Ashtead up on upbeat outlook * FTSE 100 down 0.1%, FTSE 250 flat (For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window) Dec 8 (Reuters) - London’s blue-chip FTSE 100 index fell on Tuesday as growing fears of a no-deal Brexit dominated early trading on a day Britain became the first Western country to start mass-vaccinations to prevent coronavirus infections. The exporter-heavy FTSE 100 fell 0.1% by 0919 GMT despite a weakening pound, after hitting a fresh nine-month high in the previous session. With just over three weeks before Britain completes its journey out of the EU, leaders are to meet face-to-face to try to seal a post-Brexit trade deal to govern $1 trillion in annual trade after failing again to narrow their differences on Monday. The timing of the meeting is yet to be confirmed. “Brexit remains unresolved despite extensive talks with an apparent deadline fluctuating between Wednesday and Thursday this week while efforts to get a bi-partisan stimulus package away in the U.S. continue,” AJ Bell Investment Director Russ Mould said. “How both these scenarios play out are likely to set the tone for the last few weeks of 2020 and the first part of 2021.” The FTSE 100, however, is on track to record its biggest quarterly gain since 2010 after being boosted by hopes that a working COVID-19 vaccine would spur a global economic recovery next year. The mid-cap FTSE 250, considered a barometer of Brexit sentiment, traded little changed. Britain began rolling out the COVID-19 vaccine developed by Pfizer and BioNTech, becoming the first Western country to start vaccinating its general population. Meanwhile, data on Tuesday showed British retail sales growth slowed in November as stores were shut as part of a new four-week lockdown. Among individual movers, rental equipment provider Ashtead jumped 3.5% after raising its annual outlook. (Reporting by Shivani Kumaresan in Bengaluru; Editing by Subhranshu Sahu and Saumyadeb Chakrabarty)