A letter to editoral office of a journal

Thanks to the editor and reviewers for their you for your [2] consideration and encouragement attention towards our work, we have found the comments incredibly useful in refining our work. valuable and impressive. We have considered [3] the reviewers’ comments carefully; and consequently have subsequently the following improvements have been made amended the paper in line with the advice given. We hope that these changes have improved the quality of our argument.

Again, we would like to thank the reviewers for their productive comments; we greatly appreciate the assistance they have provided us.

Yours faithfully [if addressed to a generic 'object', like 'the office'] / Yours sincerely [if addressed to a specific person]

[1] It is better to address this to the editor, by name, e.g., "Dear Professor X" (I personally tend to be more informal, I don't think it is necessarily bad to write "Dear John", especially not to a journal editor in the UK/US, you are peers after all :)

[2] Although you have addressed it to the editor, "your" here will be taken to imply the reviewers as well, who do the bulk of the work! (I say this as a peer reviewer!)

[3] Past tense, you've already completed the action.

Note: I've changed the style to fit to what I'm used to seeing and what I'm used to writing, in similar circumstances, therefore, unless noted, the majority or the changes are 'stylistic' and not necessarily grammatical.  

Good luck with your resubmission! :)