The probation service will do its best to accommodate people who are in work and who have to keep appointments with them. After all, one of their aims is to rehabilitate offenders and gaining employment is an important part of that t
process. The last thing they want is to jeopardise somebody's work prospects by insisting they keep appointments they cannot make because of work committments. How they manage offenders in that respect is up to them.
However, curfew requirements directed by the court cannot be varied by the probation service. If a variation to the hours of curfew is needed (for whatever reason) the offender has to return to court to get permission. The probation service will usually support the offender at the hearing if the reason is valid and genuine.