Extra Fibre speed issue

[#1]

I had the cheaper fibre broadband for a few months and whilst a big improvement over standard broadband, it was disappointing compared to what was promised.  In the last few days I upgraded to Extra fibre broadband and whilst slightly faster (especially uploads), it still isn't anything like what is promised.
Upload Wifi speeds on my 2008 Toshiba laptop and Samsung Galaxy Note are currently in the region of 20Mb/s with the website/app of Speedtest.net, and uploads are about 15Mb/s.  On my Xbox 360, I  downloaded a game via ethernet and calculated a speed of about 12Mb/s.  The download speeds are consistent and don't change much.  My estimated line speed is 54Mb and current line speed is 61.6 Mb, according to https://portal.plus.net/my.html?action=data_transfer_speed.
My router is a Netgear N150.
Am I demanding too much or is something not quite right?

[#2]

welcome to the forums theambler
have you run a bt speedtest? http://speedtester.bt.com/
that will give you a good indication of your download and upload speeds and what BT have your profile as.

[#3]

Via ethernet, I get 58.36 Mb/s download, 5.2 upload and 51 ms for the ping test.  So, all performing well (although it is weird that my upload speed is lower than what was tested on other speed test sites).  Is it the case that In the 'real world', about 20Mb/s is what I can expect?

[#4]

WiFi is slower than ethernet, which might explain why it's slower. What does speedtest.net say on ethernet?
I get 34Mps on wifi but 63 on ethernet, to give you an idea of the difference

[#5]

My line is capable of running around 75/16, and does so on various speedtests - but only if using ethernet. With WiFi, I'm limited to around 24/15 - when on the 54Mbps type of WiFi.
I've also noticed that top speeds on WiFi very much depend on the age of the system involved - older systems are slower.
You are probably encountering similar limits.
I don't use Xbox, but it seems a common report that Xbox downloads do not max-out the line. Others can probably give better feedback there though.