Trying to imagine the noise you are hearing and only options I can think of are:
a) It's raining
b) It's the clutch - I find the release sub-optimal, although I have now got used to it and tuned it out - kind of judders at low speed, which could I guess, sound like rain on the front window.
c) If you have a C4S, it could be the diff doing things to transfer power - more likely to hear something at low speeds as changes in transfer will be more sudden.
e) If you are turning hard at full lock whilst at low speed, the tyres tend to rub on the wheel arch (I think) which does make a sound perhaps as you describe.
d) Alternatively, of course, it could be a thousand tiny leprechauns running up and down the front of your roof...
More seriously, I don't seem to have this (I don't think) - I will listen out next time. The only moving parts in the front of the car are the steering/wheels, brakes, mirrors, wipers/washers, viscous coupling (C4 only), and the fluid circulating around the radiators, which I can't imagine making such a noise - there are no fans or anything like that in a P-Car. There are also the bits in the PCM/Hifi but there would be something wrong big-time if that made such a sound. Still stuck - perhaps the power steering? Hmmm.