By William James and Muvija M LONDON (Reuters) -Britain’s P&O Ferries on Thursday made 800 staff redundant with immediate effect and suspended crossings for the next few days, sparking a backlash from politicians and unions who criticised plans to hire cheaper agency workers instead. The shock move caused delays around Britain’s busiest port, Dover, and drew threats of a standoff as trade unions urged their members to defy any instructions to leave P&O ships. The government condemned the way P&O handled the announcement. P&O’s move was also denounced by unions and described as a public relatio…