BRUSSELS (Reuters) - Talks between Britain and the European Union on their new trade relationship made little progress this week, EU sources said on Friday, with persistent differences on important areas weighing on chances for a deal by the end of the year. That is when the status-quo transition period which followed Britain's departure from the EU in January is due to end. Both sides are now locked in talks on new cooperation rules from 2021 on matters ranging from trade to fisheries to..