Yes you can downgrade from Win8 to Win7, just Google it and you will find all manner of ways of doing it BUT it is a downgrade and my own feeling is that you will lose out if you do so. Windows 8 boots up really fast and many of its features are really attractive.
The one feature that I liked about Win7 was having the start button, the list of All Programmes, easy access to the Run Command, the Control Panel and the taskbar that we have taken for granted for so many years and I found that I could have that (and boot into the Desktop if I wanted to) by buying Start8 from Stardock You can try it for free and then buy it later if it suits you. In US Dollars it is $4.99 but I am not sure how much it is in UK Sterling - perhaps as you get to the Checkout it will tell you that, my guess is around £3.50.
I find that I now have the best of both worlds, a fast boot up (into the tiled screen of my choosing as I quite like that) and then when showing the Desktop I have the Start Button and the old Win 7 look.