The claimant will have completed this form:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/688466/n180-eng.pdf
As you'll see, Section D invites him to nominate a location for the hearing (and to provide his reasons for choosing that location). However you'll also see this guidance note on the form:
"If your claim is a designated money claim the case will usually be transferred to the claimants preferred court or the defendants home court as appropriate. However, there is no guarantee of transfer to this court. For further information see CPR Parts 3, 12, 13, 14 and 26".
If you want to try to work your way through the complexities of the Civil Procedure Rules, see here:
https://www.justice.gov.uk/courts/procedure-rules/civil/rules
However it's probably still most likely that the claimant's choice in this matter will stand.