A requested person has a right to be granted bail, unless they are unlawfully at large from the requesting Country. The lawyers acting for the requesting Country will normally argue against bail being granted by trying to persuade the Court that the person will fail to return to Court if released, (other reasons for refusing bail can be that the Court fears the requested person will commit offences while or bail or interfere with witnesses). For this reason it is important that evidence is given to the Court that the requested person has close ties to the UK, for example by showing they have a permanent job, family responsibilities and ties to their community, to show that the person is not likely to abscond.
When considering bail the court also will often expect a person to act as a security (by giving a cash deposit to court) or surety (someone who comes to court and promises they will pay the court an amount of money if the person absconds). If the requested person then fails to return to court, the person offering the security or surety is likely to lose all or part of their money.
In cases where a person has already been convicted in the Country that is requesting their extradition (especially if they face a lengthy sentence), it is harder to convince a Court to grant bail.