No. of A-level

All the Russel Universities prefer 3 A--Level, i thought it would have been fine if i take Computer Science and Math A-level along with ICT(BTEC) but then i wont be able to get into russel group universities.
Does this mean that I should either take take extended BTEC and one Alevel or take 3 A-level at once
There is physics I feel like I wont be able to keep up with CS, Math and Physics Alevel.
Is it worth taking 3 A-level or should I just do BTEC? I really want to into any russel university
Please can anybody guide me

Why do you need to go to a Russel Group university? Employers are only interested in skills and knowledge, not where you studied. There was a thread on here a few days ago from someone with a 1st struggling to get a job. So focus on skills and knowledge required to get the job you want rather than chase the vanity of prestige which ultimately counts for nothing.
Good luck!