Turn mains water off.
Lift lever arm up underneath you will see a small hole. Insert metric Allen key, turn anti-clockwise to unscrew. Tap handle should lift off.
Lift off dome with hot & cold markers.
See head of cartridge. Remove chromium sleeve. Difficult to remove. I used a blade to insert between body of tap & sleeve. See cartridge retaining nut. You now need an adjustable spanner approximately 38mm to remove nut.
Inside is cartridge. Attach mull grips to square section tap spindle & lift out strait upwards.
Once out, either replace cartridge (so far we have not been able to find one) & rubber seals. Screwfix sells a box of plumber seals for £14.99. A plumbers merchant might have individual seals for sale but our local ones didn’t. Not very helpful as they want to sell you another tap. If tap is leaking at base of tap you will have to remove entire tap inc tap tails & replace seal on underside of tap body. Use silicone grease. There are 40mm universal cartridges, also from Screwfix, that could be adapted. Not ideal but should do the trick. Hope it helps. Im still on the look out for cartridge before I attempt to adapt the universal. The leaks were stopped & tap is functional but as the cartridge was broken I would like to replace it. If anyone knows a source please post info.
Windle, August 2019