Maybe this would be better moved to private flying. I don't really think £4,000 will gain that much interest to tide you over in later life. Using it now to get your foot on the first wrung of the ladder of your chosen career may in the long run secure you a job quicker. A low end career pilot will make say £20k in the first year. How many years will you need to leave your £4k in the bank for to make £20k? ...................... MANY is my guess.
My biggest regret was listening to my parents harp on about saving for later life. I wish I had started flying many moons before I did. Tell your mum its your money, your life and your ambition and phone the flying club today.
My opinion ........... Go for it! Either now or when you finish Uni.
(Standing by for some flack from Felix's mum, please don't come after me with a rolling pin)
Good luck in wahtever path you choose.
S