Nils Melzer, the UN special rapporteur on torture has said that Assange is not held in solitary confinement at HMP Belmarsh. Melzer objected against the limited ability of Assange to prepare his legal case.
It seems that John Shipton (father of Assange) used therm solitary confinement to describe situation where Assange's access to outside is limited to his lawyers and family.
I thing Assage is currently in the the prison’s medical ward.