Another important question to ask is why/how you didn't see or realise any of these faults when you viewed the car? Did you even test drive it?
Did you miss the part when i said i'm an idiot? I went to view the car and it was in big warehouse with maybe 60 other cars and it was 4 cars deep it had took me twice as long to get there due to traffic and they were close to closing. The guy got the key, opened the door with the physical key and started the car right away. Now i thought nothing of this and just assumed he was showing me the engine running . What he was really doing was making sure the alarm didnt go off, once the engine is running you can open all doors bonnet etc and the alarm wont go off. When i was there the exhaust sounded ok, a little louder than expected but i thought that was due to being indoors and as there were cars next to it caused the sound to bounce off the cars. However it didn't sound anywhere as bad as it did when it arrived.
I didn't check the brakes or oil etc as it had been MOT'd the day before and it had been serviced 3000 miles before. And as i asked him if there were any problems with it and he said no i took his word for it unfortunately.