help me my r25 is having problems with kangarooing and rear wet footwell?

please can someone tell me how i stop my crappy rover 25 car kangarooing in the damp weather in first gear mainly but also second n even third sometimes, seems to be ok once the car has warmed up but depending on the weather can go on all day iv had the spark plugs changed an it worked fine for about a month and then was the same again its been like it all winter and no matter who im taking it to they cant seem to get to the problem and i cant afford to keep spending money on it, also the rear footwell behind the passenger seat is pemanently soaking wet iv had the door seals replaced and checked and there is no sign of it coming from anywhere, and cant work out where it is coming from pleaseeeeeee someone help me as i dont wanna get ripped off anymore than i have and need to get it fixed once and for all as i cant afford to buy a new car either at the mo, any feedback would be very appreciated xx