I took chem math phys russian.
And got offers from all top unis in aerospace field ( didn't apply to cambridge and imperial)
When I went to open days ALL uni students said that further maths is kinda waste of time, because they all just begin thought that again during first year.
And during my interviews all unis liked that i also can do something else that is not related to science only (foreign language).
So what I know so far:
It will make first year much easier so you have more time to socialise i guess..
It will deffo boost your application because i believe its the hardest a-level ( probably essential for oxbridge and imperial)
However nobody really expects you to have it at uni, so everyone will be thought this during 1st year.
Conclusion: helps a lot but on the flip side everyone will be brought to the same level, so for me personally it's not worth it unless oxbridge, imperial.