Can't improvemuch on Alan's answer.

Here in Northampton we have some bus lanes that are 'at all times' (in spite of no night time buses). Clearly those apply on Bank Holidays.

Others are Monday to Friday/Saturday and 'with flow'. They'd apply on BH Monday unless excluded.

A bus lane without any times is always enforce. A bus lane with times is enforce according to those times including bank holidays.

Unless you find one that says otherwise, which i've never seen.