Suggestion:
Yes, a rogue site in UK has been scamming immigrants and others alike in property rental scam.
Though it is not particularly targetting immigrants, large number of immigrants looking for houses have become its victims.
All foreign nationals immigrating to the UK and searching rental accommodation have been warned by NLA(National Landlords Association) about the ongoing scam at the site Gumtree.com .
The website of gumtree is an online classifieds site which defrauds innocent overseas nationals by inviting applications for rental accommodations to live in the UK.
Once the usual e-mails are sent to the foreign nationals in the UK, potential tenants are then required to submit the asked rental amount to the landlord.
However, its here the harrowing tale of woes unfolds for the unsuspecting tenants wanting accommodation on rent to stay in the UK.
After the amount of rent is sent, the tenants try to contact the landlord for getting keys of the rented property but find that contact cannot be established with the landlord because they have been cheated and the landlord does not exist at all.

{ 1 comment… read it below or add one }
Not just immigrants, it happens to thousands of British citizens every year as well. Never pay a deposit until youve actually seen the place inside and out. Never send money thru Western Union or Moneygram – those are always Nigerian scams, real British landlords have bank accts where you wire money. Even when people have seen the place, there have been recent cases of up to 5 people paying a deposit on the same property they were shown, even though the 'landlord' had nothing to do with the property
http://news.bbc.co.uk/1/hi/magazine/4685868.stm then scroll to rental scams
To be safe use an estate agent, you will pay an application fee but that's cheaper than falling for a scam and losing several hundred or thousand £s on a house that doesn't exist or doesnt belong to the landlord