Hi, check your eligibility
here The income of your parents shouldn't be included, just yours. There's always OUSBA too if there's any excess to pay, which just means paying monthly at about 5% interest - though as linin says there won't be much more than about £200 per year, which is covered by your £250 materials grant anyway.
BigFundamental makes some good points too.
I think this may come down to which modules you choose. For example, for a physics degree you could fulfil your level 1's with things like MU120 and Y162 or MST121 maths wise and still get it. However, you could also choose to do say, MST121 and proceed straight to level 2 and 3 maths courses.
So the option for the easy route is absolutely there, but of course, you are not required to do your 120 points at level 1, covering as you say, A-level and sometimes GCSE. You could do all your points at level 2 and above - this I believe is the reason why some masters programs ask for which modules you did.
If my GCSE's or A-levels were strong, I'd probably consider picking up a 10 pointer in May, just to get used to OU study and the type of answers/feedback they require, then begin with level 2's skipping most if not all level 1's.
Of course if you really love the subject, there's always the online MIT lectures, sites like khanacademy and books like Stroud to take you beyond the course material. I suppose how much knowledge you come out with at the end is your choice as long as you meet the award requirements