* FTSE 100 down 0.2%, FTSE 250 up 0.3%
* Stocks trading ex-dividend weigh on main index
* Trade worries persist after Trump signs HK legislation
* Virgin Money UK enjoys best day ever
* Go-Ahead falls after cutting regional bus division targets (Adds news items, analyst comment, updates to closing prices)
By Shashwat Awasthi
Nov 28 (Reuters) - London's FTSE 100 retreated from a near four-month high on Thursday, weighed down by stocks trading ex-dividend and as U.S. ratification of legislation on Hong Kong raised concerns that progress in trade talks with China may be undone.
The blue-chip index fell 0.2% after four straight days of gains, with Vodafone giving up nearly 4% and utility National Grid shedding almost 3% as they traded without entitlement to a dividend pay-out.
The FTSE 250 once again climbed to a near 1-1/2 year high as it advanced 0.3%. Leading gains almost single-handedly was Virgin Money UK, which soared 19% on its best day ever.
The meteoric rise came after provision for claims related to the PPI mis-selling scandal fell in line with its estimates. CMC Markets' David Madden said, given the rally in the stock, traders think a line has been drawn under the scandal.
Some traders and analysts also indicated that the Clydesdale and Yorkshire Bank owner's decision to suspend the dividend may have been a shrewd move.
Though overall trading volumes were thin, with U.S. markets shut for Thanksgiving, Asia-focused HSBC and miners weakened the FTSE 100 after U.S. President Donald Trump approved legislation backing pro-democracy protesters in Hong Kong.
The move drew condemnation from Beijing and escalating tension cast doubts over whether this would derail the attempt by the two countries to settle their protracted trade dispute.
Other losers on the FTSE 100 included equipment rental firm Ashtead which gave up 2.6% after a downgrade by HSBC.
But online grocer Ocado jumped 3.6% after plans to open a first "mini" robotic warehouse in Bristol by early 2021 signalled that its warehouse technology can be rolled out more quickly and in a bigger range of locations.
After sterling touching a near seven-month high against the euro following a YouGov poll that showed Prime Minister Boris Johnson on course to secure a majority in the Dec. 12 election, the currency recoiled, helping exporters such as Reckitt rise.
Transport company Go-Ahead Group lagged the mid-caps as it skidded 3% after mounting costs forced it to lower annual expectations for its regional bus division. (Reporting by Shashwat Awasthi and Safia Infant in Bengaluru, additional reporting by Thyagaraju Adinarayan in London; Editing by Uttaresh.V/Shounak Dasgupta/Ken Ferris)