This is my 2cents mate
Unis do look at the fact that you have done 5, which puts you at an advantage when applying,in terms of competiotn to get an offer. But once you get an offer, you can just simply stop revising for the extra subjects, and fail, but aslonga s you meet your offer you can still go.
so doing more subjects will aid in getting the offer in the 1st place.... but people are right in saying that it doesnt ake a difference AFTER ... you get the offer
thats why im going for M,FM,AFM,Bio,Chem,Physics
oh and maths is really easy... the rest have quantity (i believe)
hope that helps
source: extensive research and talking to some head of 6th forms..form some of the best grammar schools in the country