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During Q&A in English, "well" and "uhm" are two ways to begin a reply.

If you known the answer, you begin the reply with "Well... ". This creates a
pause such that the speaker can arrange his thoughts and construct the
clearest answer with good sentence structures. If you aren't sure of the
answer, but want to guess anyway, you begin with "uhm...".

In Japanese, my opinion is that it's natural to begin a response to a question
about which you are unsure of with "あの、... blah blah.".

But, how do you begin to reply to a question about which you are confident?
While I do know the answer, I want a pause so that I can arrange my thoughts.
If I lead with "あの", it could look like I am taking a guess.
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How to begin a reply to a question?
えっと is ubiquitous for this purpose. To buy yourself more time you can say
えっとですね.

そうですね is another option and carries the nuance of "that's a good/valid
question". An English equivalent might be "Right...".

You can combine the two as

> えっと、そうですね。[response]  
>  そうですね。えっと、[response]
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Or alternatively to えっと(ですね.), perhaps はい、わかりました。・・which also communicates
that you have understood the question in a positive manner.

* * *

I think your fundamental question has been jointly answered but it is worth
mentioning:

  * The way you deliver these responses is important. そうですね for example can be used to express agreement or approval if said quickly or relucutance/discomfort/thoughtful consideration if said slowly. (And in a different situation, the expression can be also used to communicate a reluctant "No".)
  * There are other responses with English equivalents. For example,「いい質問です。」would work and, if you really want to buy time, you could repeat the question for audiences benefit.
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Since you mentioned "well", `(それ)じゃ(あぁぁあーあ〜)` is commonly used for this.

Also, I don't know if it's regional or not, but in Osaka many people also use
`マー`. This is more unsure, along the lines of `あの`.
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