Yep, did it myself, not very hard either.
Run the power cable from interior mirror along headlining, down the back of the A pillar, and down the inner door seal. A credit card works quite well for this.
Then pop the side panel off the passenger side dash, and run the cabling behind.
I used the original power cable that has a male cigarette lighter fitting, then bought one of these extension sockets...
http://www.amazon.co.uk/gp/product/B004Y4KE8G/ref=oh_details_o06_s00_i00?ie=UTF8&psc=1
Cut off the male plug from the extension cable, separate the two wires and strip the covers off the ends of the two wires.
Buy an ATC fuse tap like this...
http://www.ebay.co.uk/itm/251170198363?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
You will also need a standard size ATC 3 or 5 amp fuse.
Connect the red wire of the extension socket to the fuse tap wire.
Then open glove box. There are two cut out tabs either side, push either side in one at a time and pull the glove box down gently and it will pop out of the tabs and drop down.
Take the black ground wire and crimp a fork connector to the end (I bought mine in halfords for about £2).
Look into the side of the dash by the passenger door, there is a few bolts going into the metal support of the dashboard.
Loosen the middle one off with a 10mm (I think) socket, then slide the fork connector between the bolt and metal frame, the tighten the bolt back up
Locate fuse slot number 40. It's a 20 amp fuse and is used for the original cigarette lighter.
I used this as I only want power when the car is running, not a permanent live.
inset the 5 amp fuse into the fuse tap, it goes in the slot in line with wiring, then remove the 20 amp fuse from position 40 of the fuse box and place that into the empty slot on the fuse tap.
Now put the fuse tap back into position 40 in the fuse box where you originally had the 20 amp fuse.
Then simply plug the male socket of your power cable into the female socket of the extension cable.
Tidy up and cable tie any extra wiring and tuck away behind the dash.
There is a bit of space between the rear of the glove box and the side where you ran the black earth cable
Then push glove box back into place and replace the dash side cover, you will need to pop it in place and then gently pull the inner door seal rubber over the top of the cover so it covers the edge, then push the cover back into place on the dashboard.
It sounds like a lot but is really quite straight forward.
If you get a garage to fit it, I would assume they would charge around an hours labor if not more.
Don't be tempted to just cut the male plug off the camera power cable and wire straight in, otherwise you will fry the camera as the plug is needed to convert the voltage