As you are in a small flat it is likely you are surrounded by lots of other wireless networks and your channel is clashing with some of those.
Install MetaGeek's inSSIDer
and look for a freer channel. Most users leave their router on the default channel set by their ISP. You might avoid these by choosing the extreme channels 1 or 13.
I'm surprised that you are having trouble with the signal strength of a Netgear router. I can see my Netgear DG834GT (or even the Orange supplied Siemens SE572) all round a large house. Hence I don't think it's the router itself, but more likely channel congestion.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU BB => 2010: Orange 16 Meg LLU BB