Why is my internet still bad

Well my internet has never been incredible but it has varied from good, bearable and just plain bad.
Just last week i was with TalkTalk and i was getting around 1-4 Mbps Download to 1-2 Upload speed. So it wasn't great and whenever i played online on my PS3 it would usually lag. Now about 2 years ago when i used to play Call Of Duty, I was no stranger to Connection interruptions and lag.
As i started to play Battlefield 3 I haven't lagged hardly until these past few weeks. So anyway i knew it was time for an Internet upgrade. My Dad bought an Optic Fiber broadband and i must say as soon as i used the Internet Speed Test with my iPhone it showed up as Ping 20 Download speed reached 35 Mbps and Upload speed was 1-2.50 Mbps. And i was over the moon with joy! I thought my internet would be great. However, it only showed up with these speeds when i'm by the Modem.
Once i tried the test upstairs I was getting like 2-3 Mbps Download speed? I tried it today and it came up with 10. These tests are all on my iPhone though! I tried it on my Laptop just now in my bedroom and it's not at all bad it better than before. Up here on my laptop it's about 8 Mbps Download speed. But what i really don't understand is the connection on my Playstation 3? I had no problem signing in and all it came up with the signal strength ranging from 70% to 80% Signal strength. So i thought i would play Battlefield 3, i joined a game and i literally could not play! I was running on the spot for ages, me thinking it would improve. I couldn't do anything it just had the connection interruption icon in the top right corner of the screen for ages! So please anyone? Some advice would be appreciated? Should i get the modem installed in my room? That way i can use a wire to connect it? Would that improve it? Or should i just get a long lead from the living room to my room?

OMFG! I'm in exactly the same situation! The talktalk broadband is shocking, when we got our fibre optic the speeds were slow when upstairs, however when i plugged in the Ethernet cable i got 36.5Mbp/s one thing that may help is moving the router, after some moving around i found that the speed depended on the placement, in the corner of the room was not a good place i found that on our mantle piece high up and central was the best place.
now i'm getting around 20 its still not 37 but way better than the 3, 4, 5 i was getting before
it may also be the router try and get a new one from talk talk, because it may be faulty or you could get a Wi-Fi repeater or a whole new longer range router on Amazon.