To the best of my understanding the "expired" conviction is only relevant when is dealt with within the UK.
From the act:
4 Effect of rehabilitation.
(1)Subject to sections 7 and 8 below, a person who has become a rehabilitated person for the purposes of this Act in respect of a conviction shall be treated for all purposes in law as a person who has not committed or been charged with or prosecuted for or convicted of or sentenced for the offence or offences which were the subject of that conviction; and, notwithstanding the provisions of any other enactment or rule of law to the contrary, but subject as aforesaid— .
- (a)no evidence shall be admissible in any proceedings before a judicial authority exercising its jurisdiction or functions in Great Britain to prove that any such person has committed or been charged with or prosecuted for or convicted of or sentenced for any offence which was the subject of a spent conviction; and .
- (b)a person shall not, in any such proceedings, be asked, and, if asked, shall not be required to answer, any question relating to his past which cannot be answered without acknowledging or referring to a spent conviction or spent convictions or any circumstances ancillary thereto. .
(2)Subject to the provisions of any order made under subsection (4) below, where a question seeking information with respect to a person's previous convictions, offences, conduct or circumstances is put to him or to any other person otherwise than in proceedings before a judicial authority— .
- (a)the question shall be treated as not relating to spent convictions or to any circumstances ancillary to spent convictions, and the answer thereto may be framed accordingly; and .
- (b)the person questioned shall not be subjected to any liability or otherwise prejudiced in law by reason of any failure to acknowledge or disclose a spent conviction or any circumstances ancillary to a spent conviction in his answer to the question. .
(3)Subject to the provisions of any order made under subsection (4) below,— .
- (a)any obligation imposed on any person by any rule of law or by the provisions of any agreement or arrangement to disclose any matters to any other person shall not extend to requiring him to disclose a spent conviction or any circumstances ancillary to a spent conviction (whether the conviction is his own or another's) ; and .
- (b)a conviction which has become spent or any circumstances ancillary thereto, or any failure to disclose a spent conviction or any such circumstances, shall not be a proper ground for dismissing or excluding a person from any office, profession, occupation or employment, or for prejudicing him in any way in any occupation or employment. .
(4)The Secretary of State may by order— .
(a)make such provision as seems to him appropriate for excluding or modifying the application of either or both of paragraphs (a) and (b) of subsection (2) above in relation to questions put in such circumstances as may be specified in the order; .
(b)provide for such exceptions from the provisions of subsection (3) above as seem to him appropriate, in such cases or classes of case, and in relation to convictions of such a description, as may be specified in the order. .
(5)For the purposes of this section and section 7 below any of the following are circumstances ancillary to a conviction, that is to say— .
- (c)any process or proceedings preliminary to that conviction, any sentence imposed in respect of that conviction, any proceedings (whether by way of appeal or otherwise) for reviewing that conviction or any such sentence, and anything done in pursuance of or undergone in compliance with any such sentence. .
(6)For the purposes of this section and section 7 below " proceedings before a judicial authority " includes, in addition to proceedings before any of the ordinary courts of law, proceedings before any tribunal, body or person having power— .
(a)by virtue of any enactment, law, custom or practice ; .
(b)under the rules governing any association, institution, profession, occupation or employment; or .
(c)under any provision of an agreement providing for arbitration with respect to questions arising thereunder; to determine any question affecting the rights, privileges, obligations or liabilities of any person, or to receive evidence affecting the determination of any such question.
The implication of this means that when someone does a background check on you the conviction will come up. However, unless it is specifically excluded by law it cannot be used against you by anyone who's subject to the UK law and this act. The thing is Chinese are not subject to UK law when reviewing your visa application to enter China.