I've just completely rebuilt a corsa 2005 1.2 lump
2000 to 2003 is x12xe chain driven ,(water pump is aux belt driven)
2003 on is z12xep twinport ,chain driven ,(water pump is aux belt driven)
tf the chain is too loose , it will rip chunks off the chain cover ,
(nice chunks of ali pumping round the lump ,)
hydraulic lifters collapse or stick (top end tick),cams can snap,
there are water ways going through the timing chain cover (which can leak into the timing chain ,(giving the impression the h/gasket has gone)
when re-fitting the timing chain cover(new gasket a must) ,you must have the sump off ,or you put strain on the oil pump .
there is a presure relief valve in the oil filter housing (front of engine) can stick.
the 1229cc 79bhp (z12xep) and 1364cc 89bhp (z14xep) share the same block ,cylinder head, headgasket ,only difference is crankshaft /longer stroke.
(so a 1.2 head will fit 1.4 and vice versa )
both have a very thin mls head gasket, so block deck and head must be bang on true
parts are cheap
I know nothing of the cdti dirty diesel item