I don't see anything wrong with a mini-introduction (like the one you posted) before you jump into your analysis, so long as it isn't excessively bloated and long. If it's short, and concisely sets you up for the rest of your essay, it's a brilliant way to start. It's also much easier and cleaner, in my opinion.
I'm pretty sure the majority of essays in the examination report contain a mini-introduction/thesis, so I don't think there's any fault in it.
As long as you don't start waffling on about irrelevant information such as the background of the author, the period of time, etc. it shouldn't be an issue. If you stick to just quickly stating what your "contention" is within the context of the passages, you're fine.
Mind you, there's no set writing structure in Literature, so the examiner isn't going to open up your exam and look at the introduction and be like, "well, guess you've lost 5 marks for that." It's just about your ability to coherently express an analysis/view on the passages, regardless of how you structure it, because that's solely up to you and however you choose to do it. So long as its effective, you get the points.