It's a shame what I thought was a very helpful post to OP got immediately deleted by MNHQ no doubt instigated by someone who had nothing else better to do in life than watch these boards all day long. That's because I had "contravened" some Talk Guidelines or other. Well really, because of just one [factual] sentence out of the scores that I write, that's what MN told me.
But it takes more than a deletion to deter me from passing an important message and therefore, here it is again, albeit with the "offending" sentence removed:
Just an acknowledgement to say @MECC, nice to see you popping up again at your own thread. And I can fully understand your absence due to leftist detractors who have not the foggiest of ideas how these premier public schools work and therefore, have not a pea to offer for advice, instead, making a conscious effort here to sabotage your thread. [Line removed]
Now, back to your queries. Much have been said about the pros and cons about single-sex schools. Like you, I'm an ardent supporter of single-sex education solely and purely drawing from personal experiences. I went to one since Day One at primary school right through to the end of secondary education aged 16-ish. When I went to a co-ed school for Form 6 because previous school didn't have them, my academic concentration took a bashing of biblical proportion because of distraction from the opposite sex. Still remember getting a big fat goose egg, 'Zero' - 'Nil-Pwa' - in one of the test papers after all these years! 
At least 3 of the schools here are located right in the middle of town/city or High Street (don't know about WinColl) and therefore, boys see and interact with the general public - men and women; males and females -everyday of the year. The schools concerned are not exactly a monastery with closed doors with monks living inside by themselves totally oblivious to the world outside. On the contrary, Eton, for example, is a tourist hotspot with coach loads of visitors coming from the four corners of the globe regularly to have a peep at this world renowned greatest of schools. You should see for yourself some of these tourists, especially the teenaged girls from the Orient (Japan, China, Korea, etc) getting all highly excited when they meet up with the young Etonians in the vicinity. Many will demand a selfie or two taking the opportunity to hug and get up close and personal with these innocent handsome young lads in their superb uniforms - the smartest school uniform in the world if you'd asked me.
A boys' school it may well be, but take a quick look at the School's 'Fixtures' booklet (a posh name for nothing more than a detailed diary; remember - the school does everything with Excellence) and you'll see dates allocated for different year groups (Blocks) to travel to other Girls' boarding schools in the area or slightly further afield for socials and other events. And the visits are returned in kind on other dates when girls visit the boys at Eton.
Plays, concerts, musical and other productions are a big thing at Eton! On average, stage plays alone will take place on more than 20 occasions spread out throughout the three terms. Often, girls from other nearby schools or other boarding schools join in for the productions and take the female parts. So, plenty of opportunities for the Etonians to meet girls during rehearsals and the actual productions.
Another myth about lack of females at the school dispelled and unceremoniously consigned to the dustbin!