I'm just going to lay it down here since no one has really mentioned it properly:
The Physics course is specifically designed at A Level to guarantee that those who do not do Maths and those who do/FM, are just as likely of getting a good grade. Of course, in the grand scheme of things, those who do Maths and FM will most likely do Mechanics that will help with Physics, and will, at the end of the day get good grades, but the point of this is that not doing Maths in no way restricts your own ability to attain those same grades.
The actual Mechanics itself is specifically designed to not exceed Grade 7-9 GCSE standard, particularly in AS.
Of course, in A2 you will likely come across some slightly new concepts, like the logarithm, however conceptually these shouldn't be too challenging for you, I'd suggest looking at the spec for the board you plan to do Physics on and seeing the level of demand for Maths, it most likely will be to high grade GCSE standard, meaning they can't really assess you for content that is taught beyond that unless it is taught board wide first. When I took a peek inside my formula book last week, containing both AS and A2 stuff, the symbols and letters looked funny and intimidating but the actual maths was fairly basic!
You will soon come to find that in Physics A Level, the tough bit is not the Maths, but infact finding using your own Physics knowledge where and when it can be applied! This is one of the main reasons that doing Maths does not automatically guarantee good Physics grades, you may be able to do Maths like a whizz but if you don't know when and where to apply your stuff in Physics, you're toast.
In terms of my own experience (albeit not very neutral standpoint as I do Maths and Further Maths), I'd say that the Mechanics in Physics is very easy to understand once you get the conceptual knowledge. The tough bit is the electricity for most, however it's not the equations themselves, just again where to apply, some of which, like V = IR, or Rt = R1 + R2 + R3 (for series), you may have come across in GCSE. Infact, if you did new-GCSE, you come into the AS in a very good position, as some of the AS topics like Taking Moments, etc, are now in the new GCSE, so you should be fine.
In conclusion, sure, Maths is a good option to pick with Physics, but not taking it does not inherently strip your chance of good grades, you just need an aptitude and passion for it.