Firstly, I'm not trying to rain on your parade, but usually to be a translator or interpreter for the big institutions, namely the UN or the EU, you are requirement to have more than one other language. Now, I believe there are exceptions if you're a translator (exceptions, which I'm not entirely up-to-date with unfortunately), but it's worth having that borne in mind throughout.
Secondly, if your aim is to do a degree in German from scratch (Ab Initio) as the main subject of your degree, then there are few courses in the UK which would facilitate that. I believe UCL allow you to do a straight German BA from beginners, but the grades required from your A-Levels for that degree will be in the AAA-AAB range I should think, but take a look by all means. Usually, if German were to be the major of your degree, you would have to have taken it to A-Level, or at least AS level. It is entirely possible, although it will take some research and potentially some ringing of the universities to double check, to take a degree with a major of, say, Politics, then to do Ab Initio German as a minor, and I believe there are many options to do that. The caveat to this would be that they usually require a language, doesn't matter which, to A2 level, although this isn't the same everywhere and some only require a GCSE in a language to a specific grade.
Just hunt around and start using the UCAS Course Search tool to look for degrees. When I was applying for my degree, we were more than welcome to email the admissions or languages department of the universities to ask questions such as this. If your desire really is to go on and be a translator or interpreter, it may be worth looking at other languages as well because the more, the better when it comes to a job like that.
I hope this helps in some way. I took both French and Spanish to A-Level and I understand how difficult they can be.