Ford used the same body on its Focus from 2011 until the model was replaced in 2018. On that basis, the front door from either of the cars you’ve listed should fit your car perfectly. You don’t even need to worry about finding a door from a sedan or hatch as opposed to a two-door Focus, as Ford didn’t offer that model in Australia in a two or three-door (which would have had longer doors). Even the sportiest Focus, the ST, was a five-door hatchback. Ford did give the Focus a mild facelift in 2015, but the styling changes were restricted to the front and rear, with the doors not altering at all.

Finding a second-hand door shouldn’t present too many problems the Focus sold in reasonable numbers and many ended up in recycling yards. You might even strike it really lucky and find the door in the same colour as your car which might negate the need to have it painted.

Your car requires an octane rating of 91 RON and, to be honest, the biggest difference in using the more expensive 95 or even 98 RON brew will probably be to your wallet, not the car. Changing to a higher octane rating is not really a scientific way of fixing problems like rough running, and there’s probably another reason for the poor performance.

I’d be scanning the car electronically for a clue to what’s going wrong with it, but bear in mind rough running can be caused by lots of things. If you really want to pursue the fuel you’re using as a potential cause of the problem, rather than change to 95 RON, change the service station you use. Sometimes, a service station can have contaminated underground tanks and this can cause all sorts of running problems by the time the dirty fuel is in your tank. Another hint: If you see a fuel tanker delivering fuel to a service station as you pull up to refuel, find another service station. The fresh fuel being pumped into the underground tank will stir up all sorts of nasties that would otherwise settle at the bottom of the tank. By filling up immediately after the station’s tanks have been filled, you stand a good chance of buying a tankful of dirty fuel.

The dual-clutch automatic transmission in the Focus had issues, so I would urge caution in buying one. It can be fixed if it fails, but it would be costly.