So apply the Cacti patch to the LAMP ISO rather than creating LAMP from Core then Cacti from LAMP (you get to miss a step). The other thing to consider is that the patches are getting quite old so perhaps it will need a little tweak?
Although obviously none of that will actually fix the problem that you currently have re accessing the repo behind your proxy. I have little (read: no) experience working behind a proxy so I can't really help you there. It seems strange though that you can use apt ok from the commandline but that it doesn't work in TKLPatch. TKLPatch creates a chroot but I wouldn't have thought that would cause any problem.
Now that official TKL LAMP is available use that as base
So apply the Cacti patch to the LAMP ISO rather than creating LAMP from Core then Cacti from LAMP (you get to miss a step). The other thing to consider is that the patches are getting quite old so perhaps it will need a little tweak?
Although obviously none of that will actually fix the problem that you currently have re accessing the repo behind your proxy. I have little (read: no) experience working behind a proxy so I can't really help you there. It seems strange though that you can use apt ok from the commandline but that it doesn't work in TKLPatch. TKLPatch creates a chroot but I wouldn't have thought that would cause any problem.