Check the tyre sidewall for the size format (for example 195/65 R15) and confirm it against the sticker in the door jamb or your handbook, then enter the full size plus load and speed rating in the search tool.
Yes, entering your UK number plate helps match tyre sizes and specifications that are suitable for your Peugeot 307 SW, reducing the risk of choosing an incompatible option.
No, you can select a local fitting partner and have the tyres delivered to that garage, then turn up for your appointment for fitting, balancing and disposal of the old tyres (where offered by the fitter).
Not always, but it is recommended to replace tyres in pairs on the same axle and keep matching sizes and similar tread patterns per axle for stable handling, especially in wet UK conditions.
All-season tyres can be a strong year-round option if you want better cold and wet performance than summer tyres without swapping sets, but drivers in areas with frequent snow may prefer dedicated winter tyres.