thanks vdub.. to help simplify this, my internet has always worked through wireless at home in my office (last 3years or so with o2)
the router is plugged directly into wall socket which is main point of connection coming in.
the router is on the ground floor and I am on the first floor. the direct distance from router to laptop is approximately 5m directly. it is in an open hallway down stairs. the office is just above the router but maybe 2-3m to the side.
I also keep the room door open which connects onto the landing and downstairs hallway.
the connection is very strange as it will work fine for hours... then keep dropping every 10mins or so for a few hours.
o2 have tried to change the frequencies 3/4 times now, which didnt solve the problem.
o2 Have replaced the original router with a new router, but still have the same problem.
My concern is I have Virgin coming to install a new connection on friday and the router will be positioned even further away (10-15m approx)
Any help would be appreciated 
That is an odd one.
You say o2 have changed the frequencies. By this, I assume you mean channels?
Wireless signal strength depends a lot on what other devices are near by, thickness of walls, type of walls and even, believe it or not, fishtanks (lol)
There's so many things that can cause interference.
The first thing I would be doing is moving the router (if possible) to another location.
The next thing I would be doing is changing the channel. The default is usually set to "auto" or 11. I would be changing it to 1, and testing from there. It's trial and error.
Then I would be looking at compatibility issues, ie what network card you have. I would get another device and use it in the exact location of the laptop. If this device maintains a consistent connection then you've narrowed it down to the wifi adapter/network card within the laptop itself.
Is your router G or N by the way. Not that it should make much of a difference to be honest for such a short connection!
As an example, I used to live in a 3 storey house. I had a G router, and the router was two floors down from me. I maintained an consitent connection even with this distance.