Don't know about the apples opening the bile duct...but the malic acid in apples helps to break down stones so that they are easier to eliminate. You can use apples in a couple of ways....juice them and drink fresh apple juice for the week prior to your flush...or you can do an apple fast...eat only apples for 3 days and follow with a flush.
Taking a generous dose of magnesium prior to a flush will help to relax the bile duct...you can still get magnesium supplements in the UK, right?!