Yep, it's still broadband that you've got. That basically refers to the high-speed link, as opposed to using something like dial-up. My question was about how the broadband is delivered, i.e. cable or ADSL. I've got cable, but you've clearly got ADSL, which as you probably know is a high-speed method of using your phone line.
I'm probably stating the obvious but when using ADSL you need to have filters installed on all the phone points in your house so that phones and other similar devices (e.g. fax machines, burglar alarms) work properly and don't interfere with the broadband signals on the phone line.
If the problem always happens at a certain time of night I would try going to somewhere like Speedtest.net and running tests there when it's working ok, and also when it's not, and seeing what the difference is in terms of the download/upload speeds and the latency too.
Your ADSL line is shared with lots of other people in the surrounding area, meaning that if loads of people go on and put lots of traffic on it, then it might slow everyone down. The line will have plenty of capacity for you on your own, and for a few people, but not for loads and loads of simultaneous users. If it is just "contention", then unfortunately there will be nothing you can do about it.
It doesn't sound like it's likely to be a filter problem given it's only happening at certain times of day. In theory there could be a technical problem with your line and even the socket itself, but again if it only happens in the evening that sounds less likely. The evening is also of course likely to be the peak time for people using it. Do you know if your neighbours have similar problems ?
Your wireless laptop could be having interference problems with other wireless networks in the area, which is where changing channels on the wireless router could come in. But that won't affect/help the PS3 I'm afraid.