Hi I did this as I was in a similar position. Wireless was not good enough and the phone extension in the office, meant I only synced using ADSL at around 5meg.
I have now moved the router near to the main socket, and have run a 40 metre ethernet cable > click here < that goes outside the house near the main socket, up through the roof/loft, then back out and down the other side of the house, and into the office. It then connects to a small network hub. Then my three computers all connect to the hub.
My ADSL now syncs at 8meg, and I have not had a single problem in the 18 months since I did it.