Anytime you introduce more people for the same amount of jobs, you lower the average wage paid. It's simple supply and demand. Mass immigration is definitely lowering the average wage in England. People are accepting jobs at lower wages because they have no choice. Mass immigration is not a good thing.
Mass immigration lowers the average wage of workers in England. Although the policies involved for attaining this stance is complex, the reality is the amount of novice, or low-skilled workers who migrate to England will be in the same labor pool as the English citizens who have similar skill sets.
The argument here is a simple matter of math: just because there are more people working more jobs does not mean that the country (in this case, England), is generating more income from trade. Mass immigration demands the creation of new jobs for migrants, but does not necessarily increase gross income for the country itself. If you have twenty dollars to divide among two people, each of those two people with receive more money than if you had to divide that same twenty dollars among four people—simple math.
There will always be low paid jobs, and the wages are based more on qualification than racial group. More people competing for the same job may make a difference, but unless there is a visible trend of the average wage going down year over year I don't see how this could be a factor.