When to look for accommodation for next year?

It depends completely on the university. For places like Warwick, most good properties are gone by January whereas in London accommodation can often be left as late as the summer holidays and still be fine.

As for who to ask, decide on who you really want to live with and discuss it with them, then decide a a group/pair if you want anyone else.

I think we need to have found somewhere before about February time to, if we want a decent choice. We've only been living together for 2 months and the guy has only been here a month. So a lot can happen in the next 8 months, although we are all generally chilled out people, so I can't imagine we would majorly fall out. But what I explained in my opening post could mean that there's anything between 3 and 6 of us living together next year. If I start looking then find a nice 5/6 room place should I mention it to everyone ?

My personal experience is that after living together for 7 weeks a group of us decided to live together the next year, and there were no major problems. In my third year now I'm still living with three of them, and the other three I'm still in contact with. So, whilst that's something to bear in mind, often dynamics won't change all that much from now.

I would recommend, however, that you sort out a group before you start looking for houses. Then you know how many rooms to look for, and everyone can have an input in where they live. Doing it the other way round means a lot of work for you, potentially all for nothing if some people have other arrangements/don't like the house.

Fair enough. It just might be awkward if it turns out two of them don't want to live with me/us next year, which is a possibility. Which is why I thought it might be a good idea to make a shortlist of houses, which a variety of room numbers, then discuss it with them. We would then go actually look at them together. It just seems a bit pointless if we're all trawling through the same long list of houses when I know the kind of place we're after. Plus I know which area of the city to look in, as me and another of my housemates need to be in walking distance of the uni bus stop.

That's all fine. Get a group together, decide on numbers, then you can shortlist some houses and some/all of you can go look around. We had some people very involved in the process, and some who didn't really care - you can just be most involved if you want. It'll be awkward if everyone says no whatever time it happens; but it's better for it to happen earlier and when you've put less work into it.

First year for second year: November - way to keen on that, really regretted it and some friendships between the original 6 of us drifted throughout the year so we had some drop out in place of others.

Second year for third year: May

Third year for fourth year: September... (got an apartment 2 days before my course started!)