Well i applied for economics and still got all my 5 offers even with 3 AS levels.
But the 'horror stories' are a minority to be honest. Also your probably going to be doing A2 maths in year 1, so you want to fill some of your blocks up. If anything, you could be in a slightly worse position since your doing Maths & Further - On your UCAS, your likely to have 2 official AS results - Maths and Philosophy.