Hi
Yes it's possible the wet roads were to blame. I think though what we were hearing was just normal turbo noise. Probably more of a whisper than a hiss. Really hard to explain in writing.
The hot oily smell is I think oil on the exhaust. The turbo is a bit oily and the big black pipe underneath quite sticky with oil. Not losing masses of oil though. Was serviced in December, still plenty of oil in place according to the dipstick and no stains on the drive.
Will keep an eye (and a nose) on it though. Luckily have good bongo garage nearby.
The engine often smells hot and oily, it's just that I noticed it particularly near the passenger door and this combined with the "noise" put me into PARANOIA MODE. Quite a common symptom of bongo ownership I think.
In reality our Freda has been one of the most reliable vehicles I've ever owned.
Thanks for all the help.
Sara