I'm not sure why are you getting so many odd answers to such a reasonable question for I'm assuming someone relatively new to the hobby.
Based on my experience in a different city the "holiday" or "on a break" status can mean anything from (A) on a holiday (B) working down the road at another agency or (C) had a massive falling out with the agency with both parties screaming at each other saying they will never work with each other again.
You can ask the agency if they have an idea of when the WG might return. They may or may not give you an answer, which may or may not contain the truth. If you have never used the agency before don't expect much information from them, if you use them and spend £200 per week with that agency you can expect more information, but keep in mind they want to keep getting your money so if a WG has moved agency they are very unlikely to tell you that.
WGs sometimes lie to punters, agencies, themselves.
Agencies sometimes lie to WGs, punters, themselves.
Punters sometimes lie to agencies, WGs, themselves.