No evidence that thousands of migrants are claiming sick pay while abroad
According to the front page of the Express today, "thousands of migrants are enjoying seven-month holidays "on the sick"."
But the paper doesn't seem to have any evidence to support this. In fact, the paper says explicitly that the government "does not keep records on sick pay for migrant workers."
Instead, the article quotes an anonymous employer who alleges that in the last two years one employee has claimed 28 weeks worth of sick pay while working at a second job in Poland. Even if this allegation were substantiated, it wouldn't suggest that thousands of others are doing the same thing.
Employees of UK companies are legally entitled to a maximum of 28 weeks of sick pay in a three year period, if they earn at least £111 before tax per week. They're eligible for this as long as they are in a country that's part of the European Economic Area (EEA).
So it seems the anonymous employer won't need to pay out any more sick pay, as the employee has claimed everything he is eligible for.
The employer might also consider dismissing him; this is allowed for employees who've been off work for more than 4 weeks as long as measures to accommodate their return to work - such as flexible hours - are considered.