Employers don't care about A levels, the majority of grad schemes say X amount of UCAS points from 3 A levels or equivalent and even if they did say X amount of UCAS points from 3 A levels they would most probably take your BTEC as 2 A levels as that is what it is equal to.
Don't waste your time and risk your university grades on getting 2 more A levels which you don't need, if you actually needed them for a particular job then yes I would say do them but I'm almost certain there isn't a grad job that specifically requires philosophy and psychology A levels.
Just enjoy uni, don't needlessly over stress yourself in your first year, its not worth it
Also the BTEC in Business is a good qualification to have if you are looking to go into a managerial role once you graduate, it looks better than the A levels anyway, especially to an employer