PS3 help !

Before doing all that. Is it connected to you network be wireless or by wire?

If it is by wireless then connect it to the network by a cable. Wireless connections aren't the best for gaming to be honest. I know people who have given up on wireless for gaming because the connection kept dropping. When wired to the network they didn't have anywhere near the problem, other than ISP throttling and when the router itself dropped the connection.

Its wireless the router is 300mbps.

Can you try connecting using a cable and see if that sorts it out?

Yes I suppose I will have to, but I have a hatred for wires running all over house. The PS3 is in sons bedroom and phone line downstairs

So you know, the 300mbps is "ideal" and getting that kind of speed would mean having no obstructions (you know, inconvenient and unnecessary things like walls and floors) between the PS3 and router. In reality you'd be pushed to get anything LIKE that.

We've got a "pre-n" router that's capable of 108mbps and even with the special wireless dongle just 6 feet from the router it rarely sees speeds like that.

I'm going to guess here - but if you drew a plan of upstairs and marked the PS3 on it, another plan of downstairs and marked the router on it and overlaid the two, would the two be quite a long way away from eachother?

If so that would explain the connection issues you're having. Even through no more than a stud wall and a couple of wooden floors, the signal I can get in the loft here is really bad compared to the rest of the house.

Some suggestions. If the router has external aerials, try changing the angle of them a bit - that can sometimes help. If the router is right near another device like a cordless phone, try getting them further apart if you can - I believe the signals can kinda screw with eachother a bit. True or not, I don't know - but that's a bit of advice I've heard a few times.

Has this always ways happened, there is a problem with ps3 dropping out every 5 minutes and it down to an "exchange of security key", one fix while waiting for sony to issue a patch is to disable the SSID broadcast on the router.

It would take someone with more knowledge than me to say if this will be good for your situation. I have a friend who doesn't like wires trailing all over the place so he bought one of those kits that allow you to use the power lines in the house as the cables. He only uses his connection for internet access that's why I am not sure if it would be any good for gaming.

Something like this:
Belkin 85 Mbps Powerline Turbo Networking Adaptor Duo Kit- microdirect.co.uk

mine has broke before if he has an online account I think you can just log onto the new one with his online account and im nearly 100 per cent sure that all his game stats etc will be there