Hi Strawberryblonde. In summary, the majority of those who are in custody on remand are remanded in custody awaiting trial and have not been convicted of a criminal offence and hence does not have the same regime (or restrictions) as a convicted prisoner.
If a defendant pleads guilty to say one offence (like the situation you describe) but awaits trial for other offences then the Crown Judge will place that person on Judges Remand so the prisoner will follow the same regime as a convicted and sentenced prisoner.