2007 Citroen C4 Coupe VTR 1.4 Oil leaking, Low oil presure

[linasm]

Bought this car recently. Some oil was leaking close to timing belt. Did not pay attention too much as it was small leak.
Bought it cheap as had some suspension issues that most of them sorted by now. Oil and oil filter was filthy as previous owner did not change it just been topping up as far as I understood. On computer was message on neutral gear when engine war saying low oil pressure.
Changed filter and oil. Message disappeared. Drove it nicely.
Later on I have noticed more oil in same place leaking and after couple more hundred miles some oil started appearing in radiator expansion bottle. OK. Not good thing but it looks like head gasket gone.
As far I have been reading it is common thing for those 1.4l engines.
Until it was not too much oil leaking I was driving. Oil level still OK, but started getting low oil pressure messages again.
Is it possible that this message due to head gasket failure? Is it another issue coming out with this engine? I have driven less than 1000 miles from oil and oil filter change.
My friend checked computer with OBD2 scanner and was only CO2 sensor error. Everything else fine.
Any advice on this please.