Ex Oggie:
Line Checks have nothing to do with OPCs / LPCs. They are conducted on the aircraft during a normal scheduled sector.
Other poster (sorry don't know how to look back without losing my post):
LPCs cannot be replaced by OPCs. Vice versa is however correct, since an OPC is not a licence requirement by the CAA, the LPC has more content and covers all the points of the OPC and more. It is correct that IR renewals are usually combined with an LPC.