This has just happened to me, driving along and then could only get in 2nd and 3rd, turns out is the clutch slave cylinder that has gone, so its being replaced along with a clutch kit
I had a rattling noise on Monday, it sounded like it was in the front of the engine also, I stopped to check and the AC tensionier pulley had come off, annoyingly wearing the remaining belts down Its all replaced now but check the tensionor pulley