Changing cartridge in mixer tap

Hoping someone can advise. My kitchen mixer tap has sprung a leak which I presume means I need to change the cartridge in it. However, the swiveling water spout bit itself seems very loose, and turns more easily that it used to. Is it possible I just have to tighten something up?

Anyway, I've fallen at the first hurdle. I don't know how to open it up. From a youtube video I watched I was expecting to find a grub screw either under the lever part when lifted, or under the little red and blue sticker which indicates the hot and cold sides. I haven't been able to find either. What am I doing wrong? The tap looks like this:

Hi dub_nerd - did you get this sorted? You may have to prise off the "hot/cold" thingy (shouldn't be a sticker per se, but "thingy" / covering is all that comes to my mind this morning). These grub screws, as you may know are quite small, so could be easily missed. Just make sure to turn off the water to the tap before unscrewing / removing anything

No, not sorted.
I did take off the thingy but can't find any grub screw no matter how I turn it. Maybe I need to look again. I have another problem in that the undersink press was installed without ever cutting a hole to get at the water stopcock. I was hoping the grub screw (if I can find it) could be taken off to just remove the tap lever without loosening to collar that holds the cartridge in. I was hoping to see if that had worked itself loose before worrying about replacement.

Hi,
Just had a quick look at a similar tap here in the office - grub screw head is set back a bit behind the red/hot indicator, and you'll need an allen key to turn it. Flash light might be needed to see it properly.