Is it right to say Durood in English: Peace be upon Him;I speak Urdu but I say Prophet Muhammad (Sallallahu Alaihi wa Sallam).

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

It is permissible to say: "Blessings and Peace of Allah be upon him (the Prophet)" in English if it is outside the prayer. But, it is not permitted to use any language except Arabic while one is performing the prayers, because prayer is a form of worship in exact form. Furthermore, it is not allowed to change it and one should not use any non-Arabic language as long as he knows Arabic or has no need.
Sheikh al-Islam Ibn Taymiyah (may Allah's Mercy be upon him) said: 'It is detested to supplicate in any other language except Arabic. One who cannot use Arabic is permitted. But, it is against Islam to use non-Arabic expressions as slogans among Muslims' .
Allah knows best.