A level Further maths results cash in?

I did maths with AQA, Further maths with edexcel, FM isnt cashed in yet.
I would get an overrall C in FM because in AS modules i just about got an A and in A2 modules I got like an E. Can I just cash in the AS results? I know they would see I did A2 modules but can i say some of them e.g. M2 I did extra for Maths since M2 is a maths module as well. Could I first cash in M2 for Edexcel A level Maths, then cash in the rest of the 5 units for AS FM... It might be far fetched but worth a try
If I tried to do that and it doesnt work would they give me a C or do I have a choice not to cash it in at all.
Also what is better for unis, Further maths at a C or not done at all if not doing a maths course.

Anyone has any knowledge in this? Please everyone give me info