2004 Vauxhall Vectra oil leak

Check engine breather hose is not choked or soft / flattening .

And if it is soft/flattening? May I ask?

A soft hose can flatten and restrict engine crankcase venting as can any choked breather on engine .If this happens increased pressure can cause oil leaks .

I will check it out in the morning sir, it's a bit wild out there tonight. For the record, the car is running beautifully at the moment and it's on 118000 miles thus far.
I thought maybe the seal or the silicone has failed slightly? If it soft I will order a new one I guess?

Many thanks

Could also check cam cover gasket / seal not leaking .

The pipe is not soft at all...quite the opposite.

Check and clean out any breather pipes if needed and make sure any hoses are sucking o.k .On older cars like yours with that mileage , minor oil leaks are the norm and usually acceptable due to general engine wear and not worth bothering about .If there is a seal / gasket you suspect , replace it .Air intakes can also pick up any oil fumes in older engines due to general wear and tear on innards . .