OAT don't give out too much detail of their tests but only because they don't want people boning up the 'known' questions, but the topics you need to know in order to enter ATPL training are at about the following level.
For the Maths, you need to be quick and proficient at elementary mental arithmetic - adding, subtracting, multiplying, dividing - without a calculator - quickly and accurately.
You need to be able to re-arrange elementary algebra - ie, "make 'x' the subject of the following equation" when it is set out as 'y' = something.
And you need to understand sine, cosine, and tangent.
It really doesn't need to be any deeper than that. No calculus. No hyperbolic functions.
Physics is pretty much the same level. Ohm's Law. Kirchoff's Law. Wheatstone's Bridge. Basic Electricity, Heat, and Light. Elementary Work and Energy. Resolution of several forces pulling in different directions. The Gas Laws - relationship between pressure, volume, and temperature. Reading graphs. Interpolating between columns and rows from tabulated information.
That's about it.
So you can expect OAT's entrance tests to check your proficiency at about that level.
And no previous aviation knowledge at all is required. Just general problem-solving ability.