dont think you can get a 24" (a decent one) for less than £300..
with regards to keyboard/mouse/mousepad it usually down to preference you cant really go wrong with logitech..ive been using their mice for over 4 years now (mx500 > mx518 > g5) and its the mice ive used and theyre not too expensive..ive also got a logitech g15 but at the end of the day its a keyboard so just go for the one that you think looks nice..
do you play with a low sensitivity or high sensitivity? if you play with a low sensitivity then youd need something big like a qck+ ive got a highish sensitivity and i use a 5L (both steelpad) but i cant really recommend you one because something that works for me may not work for you..