I am currently studying science with the Open Uni. I am studying 90 credit points which is roughly the equivalent of just over 2 A Levels, and can apply to 5 top unis for Biology with this (have checked with them all) including Oxford.
This gives me the choice of either continuing with the Open Uni Life Sciences degree or quitting after this year with 90 credits and starting a degree at a redbrick/Oxford.
I'm not sure what's best. I love the Open Uni- the materials are good quality, the teachers on the online forums are fantastic, INCREDIBLY helpful and fast to respond, it's extremely flexible, I find the course a lot more challenging than any uni I have been to before (I am a graduate already and have studied at 2 unis for art, though not redbrick) and I am learning so much.
Plus there's a lot less debt and the option to work even full-time if you can manage it. So basically, I can either study with the Open Uni, get a full-time job, start saving towards a house and car and all that, and don't choke myself with debt, or I can go back to a 'normal' uni, be around people 6 years younger than me, not have much time to work, not able to save up for my life, in masses of debt... BUT perhaps have more networking, more career links, more practical skills and field trips and more of a social life (and the unis I am applying to are very respected for science)
There's a lot going for the Open Uni and I have found it's really respected as it makes you look extra motivated.
If you think it's for you, go for it.