Hi, I'm in a similar position to you (I didnt really find my 'thing' in high school so never really knew what I was doing with a-levels/uni and have jumped between chemistry to history to art, and started learning russian a couple of months back and i adore it and would love to study it only apart from an A in gcse german, i have no language qualifications). With Russian, you're fortunate that it isn't a common language to learn in schools so very few courses require russian and alot come with an ab initio option (manchester and I think bath off the top of my head). If you apply to a language as a single honour then you are at a disadvantage for not having the alevel, especially if it's something common like French however with a combined honours, most would ask for 'evidence of language learning ability', which your A in gcse french shows. I think with languages (and humanities), unis are really looking for passion and enthusiasm over amazing grades. If you go for a combined degree with russian (or another less common language) i think you stand a chance of being accepted.
As for courses, you could try local colleges where you can do fast track A-levels (I don't know where you're from but in Manchester, the manchester college has alot of options where you can do all sorts of courses). I think the best thing to do is contact the universities you're interested in and ask them if they'd consider you.
Best of luck!