There is more information about diarrhoea & vomiting here: http://www.patient.co.uk/health/Gastroenteritis-in-Adults.htm.
I must again stress the crucial importance of strict hand hygiene for EVERYONE. Use the alcohol gel. (Don't steal it - the 2nd floor dispenser disappeared within hours of us putting it out, and we don't have any more yet!) But remember the best hand hygiene is from thorough washing with soap and water.
We have implemented increased cleaning of bathrooms and other areas with disinfectant to help prevent spread of illness.
Individuals affected can remain infectious for up to 48 hours after their symptoms have gone, so if you have been unwell, keep up your hand washing and try to avoid contact with unaffected people for 2 days after your last episode of diarrhoea. The HPA, however, are being pragmatic and understand that this is exam time so you may have to go to your exams, so long as you fee better, without observing this 48-hour exclusion rule.
So that I do not have to keep filling your inbox with email, further updates will be posted on my blog here: http://connaughthall.blogspot.co.uk/search/label/diarrhoea and links to those posts will be published via Facebook and Twitter (@connaughthall).
I hope everyone affected feels better soon. Let us know if we can help in any way.