absent tenant

Rent Arrears

I have a tenant on LHA whose doctor wrote to me in nov 09 to say he needed to leave london for 2 months to undergo in patient treatment. He would not tell me any further details. The other housemates think it is for rehab. however middle of feb 2010 & He has not returned to the property since and i have had only one text to say he may return in march. The LHA are paying me direct now, however he is 5 weeks in arrears and there is a shortfall every month from LHA. The other housemates have anti-social issues with him , do not want him to return and want me to evict. However i cannot track him down, i have sent various emails, voicemails.texts etc re arrears. i did serve a section 21 on him august 09 after 8 weeks in arrears, although I never pursued it to court as he made the payments up . Can i now act on that one again, or do i need to serve another section 21. If i cannot contact him can i send it to property address & push ahead whether he sees it or not? sorry for so long, but as usual nothing simple! any advice big help. louise