Jogindar ji,
I don't know if there is a translation that is recognized as the authoritative English version of Sri Guru Granth Sahib. "Authoritative" may be a matter of perception.
The Akhal Takht has said that our Living Guru is only Sri Guru Granth Sahib ji in Gurmukhi (someone, please correct me if I am mistaken here).
So, while Guru Sahib's message can be translated, the result is a translation...and not Guru Sahib. I see it as like a study guide of sorts. One does not have to do formal prakash to the translation, but one should treat it as respectfully as possible.
I don't know if there is an authoritative English translation. What I have noticed is that some translations are written in different forms of English.
This line from St. Kabeer:
"As thou deemest thyself, so deem others"
Could also be written as:
"Regard others the way you regard yourself"
Personally, I find a line like "Regard others the way you regard yourself" to be the easiest to understand.
Yet, I also find "As thou deemest thyself, so deem others" to be something that sounds so much more majestical.
And, I suppose the value of the translation may depend on what dialect of English that one speaks (North American, Brittish, Indo-Brittish) as well as the overall command of English that one has, as an English word may be used when the word has two different meanings...and the meaning used in the translation may not be the word is applied in casual conversation.
Personally, I've found the web resources to be very helpful. There are a few different translations on the web, including a few different ways of romanizing the Gurmukhi script. Some are easier to understand than others.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=4210
Something I'd like to do (but haven't done yet...) is to print out and bind a web translation that has Gurmukhi, the romanized Gurmukhi, and then the English translation.
I must confess that I haven't read through Sri Guru Granth Sahib from start to end (in any language) so unfortunately I don't have one to recommend...yet.