Thank you all. Given the evidence, I agree Etisalat must be doing the caching.
A bit of googling with Etisalat in the search string brought up: http://phpdubai.org/node/9 My site already puts the relevant "no-cache" info in the header of the dynamically generated pages, but I guess this only helps with those pages and not linked images or plain-text files. I guess a proxy is the best long-term work-around.
