I am currently installing an amp in my "Y" reg focus but I need help.
Where is the easiest place to run the amp power cable from the battery, I cant see any holes that I can run the cable from the engine bay into the interior of the car...is it going to be a case of drilling a hole

 

You can go a couple of way.

If you go up inside the nearside wing there is a grommet in the door opening which you can route the cable through. It's a bit gash and doesn't look very good but it does the job.

Or the 'proper' way is to drill a hole in the nearside wheelarch bulkhead area underneath the 2 huge bulkhead connector plugs..........be VERY careful where you are drilling though as space is a bit tight and the loom for the fusebox runs right behind that bulkhead. The dozy twat who drilled the whole on my car forgot to check this and ended up putting a 13mm drill bit through the middle of said loom. I'm sure you can imagine the amount of work require to sort that out.

Suffice to say I wasn't best impressed!