Injector

If your lucky there just a fault with the leak back return pipes,
small diameter (4mm) pipes that connect to the top of all injectors.
Peugeot part,
comes in one piece,
if memory serves 1574 Q5,
and I usually renew all 4 retaining clips.
their part no is 1982 70.
Not a big job but fiddly and the clips can go flying when you try to take them out.
Might have the first part number wrong but Peugeot will know the pipe I mean.

thanks for reply but if its the injector
is it straight forward to do

Doesn't sound like an injector seat leak,
they tend to cover the entire injector with what I can only describe a crap.
basically it's a mixture of combustion gases and oil.
black/brown crud from where the injector enters h head all the way up the body.
Your pretty specific,
fuel.
the pipes that connect all the injectors together and then return from the end one are there to return excess fuel from the injectors back to the tank.
Fairly low pressure but constant.
any of the 75mm or so long pipes can leak,
or the plastic branches that fit into the top of the injectors.
and it will drench the head/injector filling up the space round the injectors.
And to be honest the hardest part is getting it clean!
I cover it with a rag then used compressed air to blow the fuel into the rag,
still a filthy job though.
If you were to do that then start it I sure you'll spot where it's coming from.
Don't know how many of these I've done.
As stated not a hard job,
filthy and very fiddly.