Also how old are most first year students in English universities?
http://www.chester.ac.uk/sites/files/che... is the University of Chester's guide so you can see from that. On the whole, it's single rooms, and the assignment will be random. And not co-ed within rooms. They don't know you and you don't know anyone else so random is the only way to do it.
Each university does its own thing. For another example, I went to Imperial College in London (part of the federal University of London - it's not now, but it was then) and that has halls of residence with all single rooms, and some houses with double and triple rooms. Only one hall provided meals - for the rest, there are kitchens where you can do your own cooking, or you make use of the university catering. (Back then, that was pretty awful at Imperial so it was an encouragement to learn how to cook! Which I have come to enjoy doing.) In my first year, I had a triple room in a student house. That was the cheapest and the three of us pretty much kept to ourselves, especially with wanting quiet to study. Obviously it meant you don't disturb the other two if you come back late at night, and you can't invite friends back. A single is more flexible that way.
The college only had enough space for the first years so for the other two years, you sorted out your own living arrangements - but by then, you know people you might want to share with and you can rent somewhere together.
Do NOT use the word "school" in England in relation to universities. They aren't schools, they're universities. Say "school" to anyone English and they'll immediately think of primary schools and high schools. The only exception is for studying medicine, where it could be called a medical school, or if it's specifically in the name, such as the London School of Economics.
The way English education works is that you go to school, and at 15/16 you sit your GCSE exams. You can leave at that point or stay on into sixth form, either at the school if it does that or at a college, to study for A levels. These are what you need to enter university, and that takes 2 years. So if a student goes to university straight away, they will be 18 in the first year. Or if they take a gap year out to go travelling or whatever, they will be 19.
We had a guy in the house who had got through school a year early, so he was only 17; Which rather put a damper on him coming to the pub with the rest of us, as we could buy a pint of beer each and he couldn't. His 18th birthday was quite an occasion!
At English universities you generally reside on campus in halls of residence for your first year before moving into privately rented accommodation in neighbouring areas for your second and third years. What generally happens is that you choose which type of accommodation you'd prefer to live in, eg. catered or non catered, en suite or shared bathrooms. Who you end up with is pretty much random, it will just be a group of people who applied for the same type of accommodation as you.
The accommodation at my university was co-ed and, to my knowledge, it is at pretty much all universities in this country.
As for ages, most first year students are eighteen. A sizable number will have spent a year re-sitting exams and will therefore be nineteen. Sometimes first year students are in their early twenties. Generally,anyone older than that will live in accommodation specifically designated for mature students, although this isn't always the case.
Most universities have "Halls of Residence" for first year students, at least. There are also many houses converted into student accommodation near universities.
Here is a link to the Chester guide. You can make a choice of the type of accomodation you prefer.
Housemates?