Internships generally begin once you've completed your degree.
im on a year long paid internship right now, mid way through my masters degree in mech eng.
im not sure we call it an internship here, arent internships usually unpaid? for me its called a DIS - diploma in industrial studies. basically involved companies of which there are many (including blue-chip ones) take on students for year long engineering placements, basically its cheap labour.
students have already completed 2 years of study, so they have a decent amount of knowledge to enable work in idustry, we get paid roughly half what you'd expect to get paid if it was a full job and it was your first year ( 12-14k is typical)
thats organised through the university. after that its usually wise to continue getting similar placements/jobs each summer. if you liked the company you worked for in your placement, and they liked you, theres a good chance you can easily go back to work for them every summer till you graduate.
my friend did this with the MoD, went back every summer, he graduated in 2006 and will be starting work for them as an engineer onf ?45k + when he gets back from his year long trip.
you have to start somewhere, and you have absolutely nothing to loose by applying for jobs and internships at companies and industries that interest you. you make your own good luck.