Horstmann Economy 7 Timer. How to remove those push fit connectors?

I'm replacing an old Horstmann Econ7 immersion heater timer. The instruction manual for it is here: http://www.free-instruction-manuals.com/pdf/p3133739.pdf

I'm keeping the old back box and the new installation just requires me to remove the 5 existing push fit electrical connectors and push the new ones into the terminals.

Problem is I can't figure out how to remove the existing 5 push fit electrical connectors. They don't just pull out. Hoping someone here can tell me what is the trick to this or is a special tool needed?

Thanks to Andy who answered tis under the electrical forum. Just needed to use a pair of pliers and pull fairly hard.