Fitting the barge out myself

Yes it is.

But remember that it takes on average four of our craftsmen, three months to complete a barge. And they have the facilities of a large boat-yard.

It is quite possible for someone with average woodworking skills to make a good interior.

These are the stages:

Paint the exterior, fit the windows and make the barge secure.
Paint the bilge and lay your ballast
Put up the battens that will support the plywood interior
Have the barge foam insulated
Lay the main floors
Run all the services, 240V, 24V, hot and cold water, central heating pipes etc.
Put up the plywood walls and ceilings
Put up the internal partitions (remembering to run cables etc as you go)
Either buy or construct the furniture you require, cupboards drawers etc.
Paint and varnish
Do the same for the wheelhouse

This list is not exhaustive but serves only as a guide. All this can be accomplished by one person working alone using only hand and portable electric tools. There are a number of guide books available with invaluable tips and hints.

There are two sayings in the boat-building trade:

An amateur builds one and a half boats

The difference between perfect and good enough is twice as long

If you choose to fit out your shell elsewhere you can consider employing your own carpenters, electricians etc.
Bring in the specialists when you need them, this ensures that you end up with a safe vessel whilst you can still do much of the internal fit-out yourself.

Remember that the electrical standards for barges are not the same as those for houses!