Mixer tap (CO11)

Kitchen mixer tap. Bought new some years ago from Aldi. Fitted this week and found it leaks from under the control lever! I bought a new one to replace it, but thought someone with more knowledge than me may be able to fix this one, or use for spares? Only fitted for about 24 hours!
Located in Brantham on the A137.
Please let me know when you can collect.