At ds1 college (Oxf) fresher accommodation totally random, no preferences asked or given. But the room charges varied widely according to the quality of accommodation. (ds1 had very nice, very new, gorgeous kitchen, en suite...= expensive!)
On the basis of "how nice" your 1st year accommodation was, plus a random number, you got a ballot number for expressing a preference for yr2 accommodation. But preferences were very vague, generally just preference for approximate blocks and price band.
Some accommodation is batched and reserved for groups, who are handled separately, according to a combined score of the above ballot!
At ds2 college (Cam) freshers were asked a preference for price band, then allocated apparently randomly. But the room charges varied widely according to the quality of accommodation. (ds2 had very nice, very new, decent kitchen, en suite...= expensive!)
In term3, everyone given a totally random ballot number and a corresponding 5 min slot to attend accommodation office, review unclaimed rooms and make a very quick selection. (Advance prep needed).
Some accommodation is batched for groups, who are handled separately, according to a combined score of the above ballot.
Ballot numbers are reversed for 3rd years.
Complicated, but all in all a great deal less stressful than finding private accommodation for years 2+ which is what happens for many students at other unis.