Assemblies

[beamends <..hidden..>]

Hi All,
I wonder if someone could help here. I'm trying to work out how to enter
the following onto the system.

I have a kit of parts that I want to offer the option of assembling for
the customer, so the assembly would be:

1-off kit
1-off assembly charge
1-off (optional) full assembly charge. 

The assembly charges are all in-house, but when I go to the "Add
Labour/Overhead" screen the Link Accounts are 1001-Stock or 1002 Work In
Progress and 5000--Materials Purchased/Imported - this doesn't seem
right, particularly as there is a "On Hand" in the lower right corner,
which implies some sort of stock holding. Adding a Service is similar,
With 4000 Sales and 5000--Materials Purchased/Imported.

I might have be going completely the wrong way of course, basicaly I
need to issue an invoice with the kit price plus an assembly charge(s)
which is pure labour at so-much-per-hour, but I don't want to "stock"
the assembly charge, just add it when required.

Have I got something wrong?

Cheers
Richard