I've noticed there's a small amount of oil apparently leaking from the join of the pipe from the turbo to the intercooler just to the left of the engine cover...the car is running okay, presumably this oil is coming from the turbo? Apart from making my engine bay slightly messy, is a bit of leakage okay/normal? As such, should I think about flushing the intercooler occasionally (like, say, for the first time in 3.5 years! ).

Pretty common, the joints relax when not under boost and allow some oil out, dont concern yourself too much about it, just a pain to keep clean.

Common one, same here. Just the car drooling a little!

oil not from the turbo , oil is from the rocker cover breather