of course many are doing the low skilled work, as they are not entitled to benefits until they have worked here at least a year, and like most people they will do any job to get some money, as you've said its a job.
but as gordie brown said 'british jobs for british workers' you have to put your own citizens first.
but there should be some controls on how many and who comes here, and that's what the gov has been doing the last few years, using a points based system, restricting the number of Bulgarians and Romanians who can come here and ending some of the scams used to get people here and scams while they are here.
fake uni's and colleges, getting a workpermit for a relative, applying for a student visa and never attending uni, umbrella companies used to get a visa, payslips etc. sham marriages, illegal immigrants marrying a european in the uk, etc.........
