Drink cycling in UK
Section 30 of the RTA 1988 states:
A person who, when riding a cycle on a road or other public place, is unfit to ride through drink or drugs (that is to say, is under the influence of drink or a drug to such an extent as to be incapable of having proper control of the cycle) is guilty of an offence.
However the maximum penalty is a £1000 fine, and there is no legal right for the police to request a breathalyser or blood test to "prove".
The only way to lose your driving license from drink cycling is if you are disqualified from driving under the Powers of Criminal Courts (Sentencing) Act 2000 which applies to *ANY* offence. AFAIK this is rarely used, and courts have never imposed this for cycling offences!