How do I get the heads off this mixer tap?

This is embarrassing - I have a dripping mixer tap, so I thought OK I'll take the tap assembly out and clean it up, change the washer etc. trouble is I can't figure out how to get the heads off to get at the main assembly...

Theres a small plastic plug underneath each tap, coloured blue on the cold side and red on the hot. Theres no other obvious cap or cover. The plug can be depressed with a small screwdriver but it doesn't reveal anything like a screw. I've tried pulling the head off when the plug is pressed in but it doesn't show any signs of moving.

Heres a picture of the tap, and of the underneath (via a mirror!) showing the small plastic plug:




Any advice much appreciated.

If there is no grub screw on the mixer tap then the head should just pull off. What you may find is there is one only place where the tap comes loose and can be pulled out.

Try moving the mixer tap slowly from one side to the other and wiggle it side to side, you should feel somewhere on the turn where the tap head pulls out.

Thanks expertboy, however I may have confused you a bit. I can get the actual top (the part where the water come out) of the tap off no problem, theres a grubscrew at the back and it pulls off easily. But that doesn't let me get at each (hot and cold) tap assembly. I need to get each individual (hot and cold) tap head off from each side. I'm sure the little plastic plug is the answer somehow but I can't figure out exactly what to do (and I'm loathe to apply too much brute force as thats gotten me into DIY trouble before ).

Thanks for any further assistance.