Entry requirements

I have been received a conditional offer at South bank university (civil engineering), currently doing level 3 access to HE a long with gscs physics and math and L2 English.
Conditional offer states that just pass level 3 access to HE with 64 points and to send them when I've got the results.
My question is; do I really need to pass all the qualifications I've stated them above or just what they asked for which is L3 access?

You need to meet the requirements in the offer. If those requirements are "just pass level 3 access to HE with 64 points and to send them when I've got the results", then that's what you need to do. Note that everything in your UCAS application needs to remain accurate. So if you told them in your application that you'd be taking GCSE Physics, GCSE Maths and Level 2 English, then you need to take those qualifications.

However, you will no doubt be ware that their main Entry Requirements page says, "You must have five GCSE passes at grade C or above – including English and Maths – to study any of our courses. We’ll also accept Functional Skills Level 2 Maths and English in place of GCSEs. If you completed your English and Maths GCSE under the new grading system, you’ll need a grade 4 or higher." That being the case, I would definitely recommend contacting them to double check whether you need to achieve a particular grade in those other qualifications.