When I peeked last year (after results), I did see a few courses on clearing. I'm not sure if I saw computing but I saw other stuff like archeology and stuff. I remember UCL not being in clearing at all but Imperial was, which suprised me.
When will ucas be available to allow you to check clearing?
Edit: Never mind...I got my answer,
A list of vacancies will be displayed on this site from Tuesday 5 August (Scottish vacancies only) and Thursday 14 August (all vacancies) until Friday 12 September. Vacancy listings will be updated continually throughout the Clearing period.