There is nothing (that I can find) that allows for a defendant to elect for a trial without a jury in the Crown Court but such trials are possible, if there is evidence of jury tampering, under section 44 Criminal Justice Act 2003:
(2)The prosecution may apply to a judge of the Crown Court for the trial to be conducted without a jury.
(3)If an application under subsection (2) is made and the judge is satisfied that both of the following two conditions are fulfilled, he must make an order that the trial is to be conducted without a jury; but if he is not so satisfied he must refuse the application.
(4)The first condition is that there is evidence of a real and present danger that jury tampering would take place.
(5)The second condition is that, notwithstanding any steps (including the provision of police protection) which might reasonably be taken to prevent jury tampering, the likelihood that it would take place would be so substantial as to make it necessary in the interests of justice for the trial to be conducted without a jury.
Althought the 2003 Act applies throughout to united-kingdom, there are also special provisions for terrorism-related trials in northern-ireland at section 1 Justice and Security (Northern Ireland) Act 2007:
(1)This section applies in relation to a person charged with one or more indictable offences (“the defendant”).
(2)The Director of Public Prosecutions for Northern Ireland may issue a certificate that any trial on indictment of the defendant (and of any person committed for trial with the defendant) is to be conducted without a jury if—
(a)he suspects that any of the following conditions is met, and
(b)he is satisfied that in view of this there is a risk that the administration of justice might be impaired if the trial were to be conducted with a jury.
(3)Condition 1 is that the defendant is, or is an associate (see subsection (9)) of, a person who—
(a)is a member of a proscribed organisation (see subsection (10)), or
(b)has at any time been a member of an organisation that was, at that time, a proscribed organisation.
(4)Condition 2 is that—
(a)the offence or any of the offences was committed on behalf of a proscribed organisation, or
(b)a proscribed organisation was otherwise involved with, or assisted in, the carrying out of the offence or any of the offences.
(5)Condition 3 is that an attempt has been made to prejudice the investigation or prosecution of the offence or any of the offences and—
(a)the attempt was made on behalf of a proscribed organisation, or
(b)a proscribed organisation was otherwise involved with, or assisted in, the attempt.
(6)Condition 4 is that the offence or any of the offences was committed to any extent (whether directly or indirectly) as a result of, in connection with or in response to religious or political hostility of one person or group of persons towards another person or group of persons.
And, for completeness, section 43 of the 2003 Act is prospective legislation (i.e. not in force) for certain fraud cases to be conducted without a jury due to the complexity and/or length of the trial.