Considering these are run flat tires, the little scratch on the sidewall is nothing. Run flats are able to work due to a reinforced sidewall. If the tire isn't losing air, there's no bulges, and it's not showing cords, there's a very good chance there's no issue with the tire.
As far as the tread goes, you really have to measure it to see what is going on. What I'm seeing in the picture you're showing seems to me to be a decent amount of tread left, though I have nothing to reference it against to tell for sure.
According to the Kwik-Fit website, it states:
UK law requires that your vehicle is fitted with the correct type and size of tyre for the vehicle type you are driving and for the purpose it is being used. ... The legal limit for minimum depth of the tread on your tyres is 1.6 millimetres, across the central ¾ of the tread around the complete circumference of the tyre.
I'd suggest as long as the tire depth is over the 1.6mm as stated, you're golden. In the picture I can believe your tires (if the rest look like what you've pictured) easily meet this specification.