This is my first post so I apologise if this is a stupid question

I have just had TalkTalk fibre installed. I get the full promised 38Mbs when plugged in with the ethernet cable but only get 18 - 19 Mbs when using wireless.
I have used inSSIDer to select the best channel for my home, have unplugged every electrical item that may be causing a problem and I don't get any improvement on my wireless speed.
I have tried both the TalkTalk supplied HG533 and the DSL3780, both provide the same speeds.
I have used various speed checkers and done the tests on my laptop, iphone5 and ipad2.
Do you think buying a better router will help or am I stuck with these mediocre speeds - I used to get 13Mbs wirelessly when I had ADSl so it seems a bit pointless spending the extra cash.
Thanks in advance for any help you provide
