I only found this because it came up in the monthly updates to the Police National Legal Data base at work.
The new "Railways and Transport Safety Bill" (due to come into effect in September) Part 5 Aviation: Alcohol and Drugs. This sets out the offences and the pescribed limits. These apply to pilots, ATCO's, cabin crew and engineers.
The main points are set out below:
PART 5
AVIATION: ALCOHOL AND DRUGS
Offences
89 Being unfit for duty
(1) A person commits an offence if—
(a) he performs an aviation function at a time when his ability to perform
the function is impaired because of drink or drugs, or
(b) he carries out an activity which is ancillary to an aviation function at a
time when his ability to perform the function is impaired because of
drink or drugs.
(2) In this section “drug” includes any intoxicant other than alcohol.
(3) Section 91 defines “aviation function” and “ancillary activity” for the purposes of this Part.
90 Prescribed limit
(1) A person commits an offence if—
(a) he performs an aviation function at a time when the proportion of
alcohol in his breath, blood or urine exceeds the prescribed limit, or
(b) he carries out an activity which is ancillary to an aviation function at a
time when the proportion of alcohol in his breath, blood or urine
exceeds the prescribed limit.
(2) The prescribed limit of alcohol is (subject to subsection (3))—
(a) in the case of breath, 9 microgrammes of alcohol in 100 millilitres,
(b) in the case of blood, 20 milligrammes of alcohol in 100 millilitres, and
(c) in the case of urine, 27 milligrammes of alcohol in 100 millilitres.
(3) In relation to the aviation function specified in section 91(1)(h) the prescribed limit is—
(a) in the case of breath, 35 microgrammes of alcohol in 100 millilitres,
(b) in the case of blood, 80 milligrammes of alcohol in 100 millilitres, and
(c) in the case of urine, 107 milligrammes of alcohol in 100 millilitres.
(4) The Secretary of State may make regulations amending subsection (2) or (3).
(5) Section 91 defines “aviation function” and “ancillary activity” for the purposes of this Part.
91 Aviation functions
(1) For the purposes of this Part the following (and only the following) are aviation functions—
(a) acting as a pilot of an aircraft during flight,
(b) acting as flight navigator of an aircraft during flight,
(c) acting as flight engineer of an aircraft during flight,
(d) acting as flight radio-telephony operator of an aircraft during flight,
(e) acting as a member of the cabin crew of an aircraft during flight,
(f) attending the flight deck of an aircraft during flight to give or supervise
training, to administer a test, to observe a period of practice or to
monitor or record the gaining of experience,
(g) acting as an air traffic controller in pursuance of a licence granted under
or by virtue of an enactment (other than a licence granted to a student),
and
(h) acting as a licensed aircraft maintenance engineer.
(2) For the purposes of subsection (1)(h) a person acts as a licensed aircraft
maintenance engineer if—
(a) he issues a document relating to the maintenance, condition or use of
an aircraft or equipment in reliance on a licence granted under or by
virtue of an enactment relating to aviation, or
(b) he carries out or supervises work on an aircraft or equipment with a
view to, or in connection with, the issue by him of a document of the
kind specified in paragraph (a).
(3) For the purposes of this Part a reference to an activity which is ancillary to an aviation function is a reference to anything which falls to be treated as such by virtue of subsections (4) to (6).
(4) An activity shall be treated as ancillary to an aviation function if it is
undertaken—
(a) by a person who has reported for a period of duty in respect of the
function, and
(b) as a requirement of, for the purpose of or in connection with the
performance of the function during that period of duty.
(5) A person who in accordance with the terms of an employment or undertaking holds himself ready to perform an aviation function if called upon shall be treated as carrying out an activity ancillary to the function.
(6) Where a person sets out to perform an aviation function, anything which he does by way of preparing to perform the function shall be treated as an activity ancillary to it.
(7) For the purposes of this Part it is immaterial whether a person performs a
function or carries out an activity in the course of an employment or trade or
otherwise.
(8) The Secretary of State may by regulations—
(a) amend this section;
(b) make an amendment of this Part which is consequential on an
amendment under paragraph (a).
Enforcement
92 Penalty
A person guilty of an offence under this Part shall be liable—
(a) on conviction on indictment, to imprisonment for a term not exceeding
two years, to a fine or to both, or
(b) on summary conviction, to a fine not exceeding the statutory
maximum.
Hope this helps.