No offence intended but if you can only manage a C at gcse then you won't be able handle university level maths. All forms of engineering require maths (at least all that I can think of at the minute). You also need to have done the separate statistics paper at gcse and at A level it is highly advisable to do further maths if you wish to do an engineering course at uni.
When I did my gcse's at school I got an A in maths and an A at statistics (well actually a disqualification because someone's phone went off in the exam, they couldn't find out who's it was and so had to disqualifie the who year in my school from that exam, thankyou very much you

for wasting three hours of my life!) At A level I got a B in both maths and Further maths. Now I am at uni and have just done my second year. First years maths I managed 65% and this year after a bad exam got 46% which lowered my average enough to drop me down onto a BEng course. I am struggling.
If you wish to do engineering at uni you will need to be up to speed on matrix manipulation, complex numbers, differentiation and integration both by substitution and parts plus more by the end of college. They do not go over this at uni. They expect you to know it and use it straight away.
At Uni you can look forward to fourier series, laplace transforms, ODE's, vector calculus and more. This is what I have had to learn so that I am able to computer program which then allows me to do finite element analysis in solid mechanics. I also have to use Laplace transforms in my control systems lectures. When you get to university level maths you will start to realise that everything you have been taught in maths so far actually does have a use.
By university you will have to remember most equations as you don't get formulae sheets like you do for gcse and A level exams for most maths based subject (for example 6 of the 8 subjects I did this year). You will also most likely have to contend with lecturers who can barely speak English, 200 odd other students, text books which can cost up to (and I am not joking here) £200 and at no point is a lecturer going to tell you that you need to do something. It is up to you.
I apologies if I make you feel bad but I would look at it this way if your college doesn't think you up to doing As level maths then they are most likely going to save you from wasting a lot of time in the long run. Alternatively if you re-sit you gcse and get an A or very high B then good luck with pursuing your engineering education.
Also as Joewb said not everything is true they told you at gcse. There is a square root of a negative number. i (or j depending whether your doing dynamics) is a very important number.
Mike