UPDATE 1 — UK Stocks — Factors to watch on September 18
(Adds new items, updates futures) Sept 18 (Reuters) — Britain's FTSE 100 index is seen opening lower on Friday, with futures down 0.2%. RETAIL SALES: British retail sales showed a surprise increase of 0.5% in August despite the latest jump in fuel prices caused by the resumption of the Iran war, official figures showed