Wireless strength/signal is influenced by so many factors it'd be nearly impossible to pin down the problem from the details you've provided. Unfortunately being a rebranded or proprietary Sky router, it is unlikely to have any external output to attach a better antenna
Really depends how much physically mass it has to penetrate through in order to reach your laptop and PS3 - depends on the construction of your house, the materials used and the interference from other wireless networks in your neighbourhood and then the quality of the end devices.
For your PS3, being stationary - it would be best if you used wired networking to connect your PS3 to your router (if it has spare ethernet ports); reduce your latency/ping during gaming. Using a RJ45/ethernet/Cat5e/Cat6 cable.
You have a couple of options:
1) A new, compatible router with higher-standard wireless (N for example) with additional external antenna(s)
2) Relocate the wireless router until you get even signal strength throughout your house - although making sure you don't put your router on a long telephone extension cable.
Ryan