Coming from someone in the industry, a "not very expensive" landscape company is generally not a great choice :-) Inexpensive fly-by-night outfits abound but they are often a) not licensed or bonded, b) don't know exactly what they are doing (anyone can call themselves a "landscaper") or c) do sloppy, possibly dangerous work and have no follow-through or even pick up after themselves.

As a designer, I work with landscape contractors all the time and it really is a case of you get what you pay for.

Yep. If you are having features installed on your property, you want a contractor. Running a legitimate contractorship costs money, you pay for that when you hire one.

I know one that has been in operation for 25 years that would make something for you that was tasteful and convincing (naturalistic), but will want to be paid for it.

And is booked until July.

I completely agree with the above.
It pays to check out what the contractor has done before. Look at his work and talk to former customers. It will be well worth your time. Nothing worse than a water feature done bad. Even some of the pros do an amateur job, usually in the rock work.
Shop around, get estimates, and check out references.
An educated buyer is a smart buyer.
Mike