Both phones are connected to the same DSL 20 meg Virgin Media WiFi connection, iPhone has no SIM installed, the i9100 is in airplane mode. Neither phone has been in any way optimised for speed and in both instances we are using the stock browser.
We decided to turn Flash plugin on in the browser on the Galaxy S II as although it is known to slow things down a little it does at least give a fuller indication of the true web experience on the phone. In fact, had we switched Flash to 'on demand' the i9100 would almost certainly have loaded the web pages up even faster.