A visa may be revoked by the visa-issuing post overseas under paragraph 30A of the Immigration Rules if (a) false representations were made or material facts not disclosed for the purpose of obtaining the visa, or (b) a change of circumstances since the visa was issued has removed the basis of the holder's claim to be admitted to the UK, or (c) the holder's exclusion from the UK would be conducive to the public good. Apart from multiple entry visit visas, a visa may only be revoked before the holder has travelled to the UK. (A visa may also be cancelled by the visa-issuing post for administrative reasons, e.g. where a mistake has been made).
An Immigration Officer at a UK port may refuse Leave to Enter to the holder of a valid visa for any of the above reasons under paragraph 321 of the Immigration Rules. Such a refusal would invalidate the visa. Leave to Enter which is in force may also be curtailed or cancelled for similar reasons under paragraphs 321A-323 of the rules.
We can only gather information about revoked visas at disproportionate cost because it cannot be retrieved centrally for technical reasons. Local searches could be initiated if a particular country is specified.