Dissertation Proofreading and Correction

I’ve already written my PhD dissertation in Spanish and an abstract in English, the latter of about 13.000 words (with word counting system), despite some of them are abbreviations or measures. I consider this is a refined work, as my supervisors have already read through it and I myself am author of 7 scientific papers. However, none of us is a native English-speaker so some sentences may be difficult to understand or sound odd and unnatural despite being grammatically correct. Also there may be some British-American coexistence, but I want it to be completely British. The dissertation is focused on adsorbent porous materials, mainly amino-modified siliceous materials. Of course, it is not necessary the review of the actual meaning of the result discussion, nor the checking of the conclusions drawn. However, it is neccesary for the work to be edited by somebody versed in the topic and who knows what he/she is reading.