Can somebody draw them?
There is no 80-150 ton barges in pakset for 18xx
Google search says they were not that unusual.
1817 (http://books.google.com/books?id=910UAAAAYAAJ&dq=barge%20tonnage&pg=PA70#v=onepage&q=barge%20tonnage&f=false) (right bottom corner)
1839 (http://books.google.com/books?id=NdlLAAAAYAAJ&pg=PA214&dq=barge+capacity+ton&hl=en&ei=Ysq4TPSVGseWOvar9f4M&sa=X&oi=book_result&ct=result&resnum=5&ved=0CEAQ6AEwBDgK#v=onepage&q&f=false) (third paragraph from top)
1855 (http://books.google.com/books?id=YAgAAAAAMAAJ&pg=PA95&dq=barge+capacity+ton&hl=en&ei=ysy4TIztDM6fOvC_qZ4N&sa=X&oi=book_result&ct=result&resnum=2&ved=0CDMQ6AEwATgo#v=onepage&q&f=false) (third paragraph from bottom)
1863 (http://books.google.com/books?id=lqUFAAAAQAAJ&pg=RA2-PA38&dq=barge+capacity+ton&hl=en&ei=Ysq4TPSVGseWOvar9f4M&sa=X&oi=book_result&ct=result&resnum=2&ved=0CDEQ6AEwATgK#v=onepage&q=barge%20capacity%20ton&f=false)(bottom of page)
These seem to be American - in Britain the canals tended to be narrow, and in any case canal transport was quickly replaced by rail in the 1800s. If you can find some references and ideally pictures for British barges that fit what you would like, I may draw them when I get time.
Well, there is no real big rivers in real-life Britain, but we can have them in simutrans map => need for bigger barges.
About models: Something pretty generic. Just current steam/diesel model scaled to Seine Netter size will be enough.
There are modern barges in Britain. They are mostly seen on the Thames and the Trent. For an example of a 1950's version see http://www.esk-dredging.co.uk/leicestr_trader.htm (http://www.esk-dredging.co.uk/leicestr_trader.htm). However, most vessels that I have seen on the Trent look like small coastal vessels rather than the barges seen in Europe or North America. (probably due to the fact that most of the route are likely to include some travel beyond the river mouth into the North Sea). The ships that are seen on the Trent are often not only small but also flat-bottomed as they use wharfs that are out of the water at low tide. Pictures I have seen of cargo vessels on the Thames seem to be more typical brages that are pushed (or pulled) by tugs.