You really dont know what your talking about do you?
For one thing, the requirement to prove that there is no Brit/EU perosn who can do your job already exists across the entire EU including the UK.
Secondly, the Tier 1 migrants visa (the one that lets you work where you want in the UK and is reserved for highly educated people) now requires a person to have a masters degree and to have earned the equivalent of £40k in the previous year - so the whole hiring cheaply skilled workers on this particular visa is not going to happen. In fact bery few non-managers get through on this visa these days.
Thirdly, in engineering most of the overseas staff you are complaining about are actually obtained through offshoring and in my experience usually have the skills and work ethic to get the job done well. If they dont there quickly replaced with someone that does!
Lastly, if UK degrees where worth anything company's might not look so regularly for the foreigners. Hell just recently, the UK gov proposed reducing the length of an engineering degree from 3 years (which is already too short to learn the skills you need to become a full engineer) to 2 years! Australia, New zealand and South Africa all require 4 years to become an engineer (and believe me thats 4 solid years - there are no easy subjects) and in Germany they require 5 (although there slowly moving to 4) to think you can become an engineer after 3 is ridiculous.
Sorry rant over... but honestly, your government already makes it more difficult for legitimate foreign workers to work in Britian then in any other country in Europe... If you cant get british people into jobs with the lack of competition this causes then obviously british people dont have the skills the companies want - and whos fault is that?