just curious , but do employers in the UK send prospective employees for a drug/alcohol screen before offering employment ? would be interested to hear from both private and Govt/County/Borough employers and employees ....usually (I think) I can spot a user/abuser during a preliminary interview and toss the application into the "round file" and it saves wasting the money of a test , but how does it work in the UK with all the rules and regulations you seem to have .
(yep, I'm an old reactionary fascist pig who has a bias against tie-dye, long hair, tattoos and piercings.......but been there and done that

)