I'm a huge Dr. Who fan so I love that you are doing these customs.
Right now, though, I'd say they are overpowered for HS. For Dr. Who they are right on. Sometimes it is hard to import characters from movies, comics, TV, etc. and keep them thematic but not broken.
HS Codex 6 has a good article on this customs philosophy. I'd recommend giving it a read. You can get it
here.
For instance, with the Cybermen....
No dragon has ever swooped down behind them and knocked them over face first in the TV show. Imagine if Charos did this. How easy would it be for a Cyberman to get back up? In other words, don't look at the perfectly scripted world of Dr. Who to develop them as HS figs. Think of what could happen in a real battle (I just referred to a dragon knocking over a robot as a real battle... I need to take a break from this game).
BTW, exactly what figs were in the pack you got and where did you get it. I didn't even know Dr. Who minis existed.
Anyhow, you are off to a good start. Hope the Codex issue offers you some insight.