Many universities have a B grade at Maths GCSE as an essential requirement, this is more to do with cutting down the number of applicants than because you'd be unable to manage the mathematical content of the degree. Unfortunately, it will still prevent you from applying for those degrees. The good news is that not all universities require a C grade, it may limit your options somewhat though.
The statistics in Psychology are mostly procedural, there is very little calculation you have to do. It will depend on whether they teach you to do the stats by hand - all statistics can be done using SPSS on the computer, so you do not need to know how to do them by hand (and when you come to do actual research you will use SPSS) but some courses like to show you the process so that you understand them better. Even in that case, the maths is easy, the difficulty is getting your head around the different terms.