By Jack Mendel Border force staff at Heathrow Airport are to strike for 23-days in a dispute over new terms and conditions. 650 members of the Public and Commercial Services (PCS) union will walk out from 31 August to 3 September, with further disruption until 22 September. The hundreds of staff will be ‘working to rule’ and will not work overtime until later next month. The strikes at Britain’s busiest airport is set to cause chaos at the back-end of the UK summer. All-in-all there will be 23 days worth of industrial action, which is part of what the union calls a “long-running dispute about …