Can anyone confirm that Socrates is as described in all of Plato's works, or is there a distinction between Plato's Socrates and the 'real' Socrates?

We don't really know.

What we do know of Socrates and his philosophy comes largely from Plato and Xenophon's writings about him. These don't exactly agree, though (read, for instance, the two different versions of the Apology of Socrates and see that there's a fairly large difference between the portrayal of Socrates in the accounts.

The two major points of view are:

• (Early) Socratic dialogues by Plato are largely accurate. (This includes, e.g., those collected in the Last Days of Socrates). Later ones (esp. those discussing Forms in great detail) are not representative of Socrates' philosophy. Xenophon is largely inaccurate except when he agrees with Plato.

• Plato and Xenophon are both largely inaccurate portrayals of Socrates, and are entirely presenting their own views in his mouth. When they agree on something, though, it's more likely to be accurate.

I can't find anything in my notes of anybody suggesting that Xenophon is largely accurate and Plato is only good when he agrees with him.

I have the impression (or had, two years ago, when I wrote the essay I'm working from now...) that the idea that Plato's early stuff was generally accurate was the most commonly held (it's sufficiently mainstream that the Penguin Last Days of Socrates has the editor put forward this viewpoint in the introduction). The "writing Socrates around their own philosophy" view, though, is put forward by Robin Waterfield.

On the Symposium specifically, I don't know much about the academic consensus, but it's from 15 years after Socrates' death, in the period where Plato's writings are thought to be moving away from being closely based on Socrates' teachings and establishing a more distinctive Platonic system of thought.

So the short answer is no, we can't really tell whether any of Plato is authentically Socratic. The stuff which is consistent with Xenophon's Socrates is most likely to be authentic, though, as is that in Plato's earliest works.

The earliest depiction of Socrates is found in the play «the Clouds», written by Aristophanes while Socrates was still alive. Once he died there was an explosion of Socratic dialogs and who even started the wave is a matter of much dispute. According to Aristotle it was Alexamenos of Theos but we have a fragment in the Oxyrynchos papyri claiming Aristotle is wrong on that point. We also have fragments of dialogues of these «minor socratics», along with the dialogs of Plato and of Xenophon.

From Diogenes Laërtius we have received a very detailed biography of Socrates along with broad overview of all the traditions which believed to be his true heirs.

Based on all that today the general opinion about the Symposion is that it is not an "early" dialogue of Plato. "early" means most scholars concede it might contain a grain of the real Socrates. Dialogs agreed to be "early" are mostly about Socrates pointing out the inconsistencies in the opinions of the others adding nothing of his own.

The Socratic Movement by Paul A. Vander Waerdt, The Cambridge Companion to Socrates by Donald R. Morrison.