Removal Of Heater Panel Wiring Query

Car is a 1999 Fiesta 1.25 Zetec and this seems like a very stupid query I confess up front. I need to replace the in cabin heater controls panel. Thanks to this forum etc I have determined exactly how to remove the existing panel by removal of the radio , removal of 2 x retaining screws , and removal of panel , followed by disconnection of heater direction control cable , disconnection of the Fan Blower Multiplug cable , and lastly the subject of my query which is the disconnection of the small White AMP 12 pin connector from rear of Resistor Rheostat unit. Now I have a replacement from scrap with wires cut off that run to that plug and my stupid issue is that I cannot figure out how exactly you remove/disconnect these plugs .. I mean I know there has to be lugs etc etc , but so help me I have this spare unit , I can see clearly .. I have good light .. I even have a magnifying glass ... and still I cannot so far determine exactly how I release these **** connectors. I am sure these are probably used extensively elsewhere and also no doubt on many other cars .. so can someone point out the stupid clue that I am obviusly missing here .. I do not want to damage the plug etc. I have prodded , poked , etc etc .. and so far at least no joy .. I want to know how to do this BEFORE I strip out the existing one for real when access etc will be more restricted....Appreciate this nugget of wisdom from someone who simply has actually done it rather than speculating etc etc .... your help is much apprecaited .. Mike