Yes, it's not very clear, is it? FA regulations appear to limit long-term loans (over 93 days) to a maximum of four from UK leagues, no more than 2 from any one club. Section 6.6.3:
http://www.thefa.com/~/media/files/thefaportal/governance-docs/rules-of-the-association/2013-14/standardised-rules.ashx
http://www.dailyecho.co.uk/sport/saints/news/11381293.taider_set_to_arrive_from_inter___osvaldo_to_go_in_opposite_direction/?action=complain&cid=13020970