What are the consequences of using these passwords to enter as another person?
Assuming the passwords were used in the way described and was unauthorised, as a minimum this would be an offence contrary to section 1 of the Computer Misuse Act 1990, (with emboldened consequences):
(1) A person is guilty of an offence if—
(a) he causes a computer to perform any function with intent to secure access to any program or data held in any computer, or to enable any such access to be secured;
(b) the access he intends to secure, or to enable to be secured, is unauthorised; and
(c) he knows at the time when he causes the computer to perform the function that that is the case.
(2) The intent a person has to have to commit an offence under this section need not be directed at—
- (a) any particular program or data;
(b) a program or data of any particular kind; or
(c) a program or data held in any particular computer.
(3) A person guilty of an offence under this section shall be liable—
(a) on summary conviction in England and Wales, to imprisonment for a term not exceeding 12 months or to a fine not exceeding the statutory maximum or to both;
(b) on summary conviction in Scotland, to imprisonment for a term not exceeding 12 months or to a fine not exceeding the statutory maximum or to both;
(c) on conviction on indictment, to imprisonment for a term not exceeding two years or to a fine or to both.
Depending on what actions are taken, there are more serious/aggravating offences at:
Section 2 - Unauthorised access with intent to commit or facilitate commission of further offences.
Section 3 - Unauthorised acts with intent to impair, or with recklessness as to impairing, operation of computer, etc.
Section 3ZA - Unauthorised acts causing, or creating risk of, serious damage.