just a quick message in the hope to be useful to someone, considering how many times I found help here
On my new splendid 147 (every day I like her more and more!) there was a quite annoying plastic rattle coming from the boot, in particular at low speed and on rough surfaces (not on bumps and not at higher speeds).
After a few tries I spotted the cause in the small black plastic "pistons" on the sides of the door, the ones with rubber ends that push the boot door up when you open it from the remote or button inside the car.
They are plastic and go into plastic, so I sprayed a good amount of silicon grease all inside and around them, a couple of times, being sure to grease them well, and since I was there I did the same on the point where the arms of the boot door are connected with the car body. PROBLEM SOLVED AND NOW IS DEAD SILENT!
About noises and rattles, I have to say that after well cleaning and greasing with silicon grease all rubber seals, doors, and all possible moving external and internal parts, now all is smooth and nice. I'm left only with a squeaky clutch pedal but next week I'm going to bring her to Richard Drake for a service and will let him deal with the pedal
Hope it will be useful for someone else!