Forensics are a no go so unless the police believe the boy is at immediate risk, the case will be carried out in slowish time. That is of course if the victim is not on any protection list, whether with the police (CPT) or social services. Sometimes these two bodies do not work in unison.
Due to his age, the victim will be videoed as opposed to given a statement. His appropriate adult would probably not be a parent, as they are aware of the case. Social services, more that likely EDT (Emergency Duty Team) will act as guardian.
The boys video will then be shown to the CPS and/or a child psychologist or pscychiatrist to diffuse any lying or obvious fabrication. The CPS can ask for additional videos for clarification, and due to the case and the victims age, can actually set the questions.
Then after a review of the evidence and history of the suspect, the case will be no further actioned or the suspect arrested.
After interview, another review by the CPS-no further action, bailed for more evidence, charged and bailed for court or finally charged and straight to court. Him being 14, it is unlikely he will be kept in overnight.
You can have bail conditions before a charge, but unlikely. Due to his age the only conditions likely to be imposed before court are not to contact any prosecution witnesses. At 14 they will not put him in care to move away until court.