Welsh plugs on a astra f seh20 how to remove them

[Jax SEH20]

Hi guys I'm sitting with abit of a problem I noticed my car was leaking water couldn't find the leak but by chance and a stream of water I found it to be at the back of the motor by the alternator and right by the knock senser both welsh plugs are leaking. My question is how do you remove them I can hardly get my hand in there I've used a temp salution (pratley steel) but I would really prefer to change them thanx

[Wayno]

Very crappy spot,u have to remove everything,alternator and rear water pipe,then with a use a hammer and screw driver to knock it on the one side till it pops