Yes. Enter your reg into the search tool to see tyre sizes and options matched to your Grandis. It is still worth double-checking the tyre sidewall or the door-plate sticker if your wheels have been changed.
Look at the tyre sidewall for a code like 215/60 R16 (your numbers may differ). Enter the full size, plus the load and speed rating shown, to ensure you are comparing tyres that meet the vehicle requirements.
Often, yes. MPVs can be heavier and carry more passengers, so the correct load index matters. Choose tyres with the same or higher load rating than currently fitted, and never fit a lower rating than specified for your vehicle.
It is possible, but it is usually better to replace tyres in pairs on the same axle for balanced grip and braking. If replacing one, match the size and ratings exactly and keep tread depth close to the tyre on the other side.
You pick a local UK garage and an available appointment time during checkout. The tyres are delivered to the fitting location, and you simply arrive for the booked slot to have them fitted.