From Collins, like hell is a phrase that some people say "to emphasize that they strongly disagree with you or are strongly opposed to what you say."
In your case, Ron says he is Scan Shunpike. Scabior does not believe him and does not agree with that statement. Scabior replies with "Like hell you are".
Greyback and Scabior knows who Scan Shunpike is (perhaps because Shunpike works for them).
"He has put a bit of work our way" suggests that Shunpike has brought some business to these Snatchers.
This phrase essentially means that someone has arranged some work for you. They have informed you of some opportunity.
In this case, I imagine Shunpike was reporting the whereabouts of Muggle-borns and Hogwarts truants (= victims) to Greyback and Scabior. It is possible that Shunpike was 'Imperiused' into doing their dirty work.
Follow up questions from the comments*: How should we understand "our way" then? Why does it not have a preposition? E.g. He has put a bit of work 'on' our way? Is "our way" a common sentence in speech?
*I am incorporating them in my answer so the information there is not lost if for some reason the comments are removed.
How should we understand "our way" then?
(1) You can think of "put a bit of work our way" as "brought us some business" or "made us aware of the location of possible targets".
(2) Another possible interpretation is that Shunpike may have literally made arrangements to set/get potential 'victims' on a path that would eventually bring them face to face with the Snatchers.
"... put a bit of work 'on' our way" is not natural/idiomatic.
The addition of "on" as in "on our way" (ignoring the adjacent words in the sentence) would imply that the 'victims' are placed on route (they have been tricked/deceived) where they would come face to face with the Snatchers.
"He has put a bit of work (= victims) on our way [to destination name]"
... would be interpreted in the following way:
The Snatchers are going from point A to point C (destination), and Shunpike arranged to somehow put the victims at point B (leading them into a trap). Shunpike has put the victims somewhere on their (= the Snatchers') way to Point C.
Having said that, there are two reasons why the "on" in "on our way" does not work here. First, this is not the intended meaning here.
Second, it would not be idiomatic, as Eddie Kal pointed out to me in the comments. As a whole, the phrase "put a bit of work (i.e., meaning Shunpike got us some Muggle-borns and Hogwarts truants) on our way" would make the sentence very unnatural and even more difficult to understand.
Without the "on" it is a general statement saying that Shunpike have done something for them. In the past, he has informed them of some victims or something of that sort.
Is "our way" a common sentence in speech?
A much better explanation of "put [something] our way" is provided by userr2684291 in the comments.
Have you heard of the expression Send it our way, or The hurricane is heading your way, or We're sending help your way, or, even more commonly, The man you're looking for went this way (here the speaker points in some direction), Go that way (same thing here)? These are all the same construction as concerns this/our/that/my/your way. Unlike this/that way, where there's still some ambiguity and you sometimes have to point (or look/move your head in a certain direction), with our/my/your way it's clear you mean "in our/my/your direction". - userr2684291
An answer to this question What does “we sent his way” mean in this sentence? in ELL says such a construct is "an informal idiomatic expression ..."