The standard usually refers to the USA (North American) release, which is fully English. However, there are fan-made "Renegade Platinum" ROM hacks that modify the difficulty and Pokémon availability.
Avoid any site that asks you to complete a "survey," download a "download manager," or enter your credit card information. The Pokemon Platinum ROM is a 128 MB file. If a site requires anything more than a CAPTCHA, it is a virus. LINK Download Pokemon Platinum English Version Rom