Portugal and France
Somalia is closest to size as that of France.
From France, Kent is the closest English county.
Excluding Scotland and Wales - the closest country to England is France.
During WW2, the countries of France, Switzerland, Austria and Yugoslavia bordered Italy on the north. NO the closest country to Italy is Cyprus.
Spain borders Portugal, France, and Andorra. One of them is the closest by land depending on where in Spain you are.
England shares borders with Scotland and Wales, so they are the equally closest European countries to England. The closest mainland European country to England, which may be what you mean, is France.
France is closest in size to Thailand. It has land area by 94% of Thailand. Thailand - 513120 square kilometers France - 545600 square kilometers