Diabetes UK have a page on managing Diabetes with illness which you can find here.

TREND produce various leaflets on Type 1 and Type 2 Diabetes.

Here you can find their leaflet on Sick Day Rules for Type 1 Diabetes.  To the right you can find a webinar they have produced on managing intercurrent illness with Type 1 Diabetes.

My Diabetes My Way have a page of sick day guidance for Type 1 Diabetes.