I've always thought of the UDI as the most right wing major party in the world, counting both social and economic issues.
They have veered to the left (or the center, if you prefer) on economic issues since the end of Pinochet's government. I think most Republicans are more economically right-wing than UDI: the UDI seldom, if ever, makes calls for reduction in spending or taxes, for example. Quite the contrary, most of the UDI voted in favor of the last sales tax hike. Many in the UDI also support Lavín's "Social Ministry" idea.
The UDI is much more conservative in social issues, of course, but they are not as politically relevant in Chile as they are in the US (although that's been changing). The UDI is certainly not extremely right-wing socially in the Chilean political spectrum. There is a lot of opposition to abortion and gay marriage even within the Concertación.