E.g. I hardly can understand Scottish accent. Need a region where people speak so that I can understand them.
Everyone has an accent. There's no such thing as a neutral accent. However, there are some accents which are considered "standard", being closest to the pronunciations you find in dictionaries and using grammar and vocabulary that are considered standard.
Things is, they aren't just based on geography. It's based on class culture and education as well. "Educated" people from middle class backgrounds have a more standard accent and dialect than people from the same area, anywhere in England. The nearest you get to 'standard' tends to be middle class "educated" people in the Home Counties, which is to say the counties nearest to London. I would say that the best bet for what you want would be Buckinghamshire, Hertfordshire, Berkshire and Surrey.