So I've removed the 2 litres of excess oil that I put in but the level on the dipstick isn't moving. It still goes above the top of the black part and onto the actual dipstick. I know the garage that I bought it from did an oil change before I picked the car up so all I can think is they filled it up WAY too much. I've done around 4000 miles in the 7 months I've owned it, some slow but some fast. I'm guessing any damage to the catalytic converter or any seals, etc. will have been done already.
Matt