Pete Waterman?
Scarborough north bay railway?
Bala Lake railway ?
Somewhere foreign?
Southern Fuegian Railway, Argentina? (That's a very long way away.)
You have more or less hit the target as far as the place of use is concerned - it was Ivory Coast and French Congo. The latter was part of French Equatorial Africa. The builders probably spoke French but weren't actually based in France!
As far as the locomotive is concerned - there are a couple of important points that you haven't got yet. As a clue - to me it looks a bit like the front of a Mallet riveted to the back of a Garratt.
Builders: this is, I feel, most probably a giveaway -- Tubize, in Belgium (the Walloon bit)?
Right area. The builders (fourteen were built in total) were the Forges Usines et Fonderies de Haine-Saint-Pierre, part of La Louviere, between Mons and Charleroi.
(Doesn't Haine-Saint-Pierre mean, literally, "Hate-Saint-Peter"? Funny lot, these Belgians...)
It gets its name from the River Haine: the river’s name comes from a variation of a Germanic word meaning ‘that which passes through the woods’. The river’s name went on to be the origin of the name of the province of Hainaut: one of the daughters of the Count married Edward III (gaining an ‘l’) and due to an imaginary connection a wood with a similar sounding old English name meaning ‘a wood belonging to a religious community‘ was later respelled as Hainault. (So she wasn’t the original Essex girl.)
Source: Mr and Monsieur Wikipedia’s site.