IJT are one of the largest UK suppliers of compatible toners.

This listing is for one of their 1250/1350 HY (High Yield) cartridges, for the Dell models listed below:

Dell 1250c 1350cnw 1355cn 1355cnw C1760 C1760nw C1765 UK

Someone who bought one of each colour has left the following Feedback:

"The toner/ink is all boxed and sealed with clear instructions in English (if you need them). Works straight off in the printer - no warning lights. Excellent."