I guess that, if you are living in University accommodation, then as the landlord, the university can let the Licensing people on-site and into rooms, in the same way they can let anyone in if they suspect illegal activity.
And if you are using a computer, wouldn't the Uni be able to tell by your internet useage? If you are using JANET, the usual university ISP, then they can check that. Or not? Using the university provided isp doesn't have the same terms of service as a commercial isp.