Your budget is not enough to be useful.! . . . I've seen this time and time again and the outcome is nearly always the same.? Weak Under performing machine that is unreliable that ends up with 1 of 3 outcomes.
#1 It's scraped and started again so the your budget is the price of learning(hardway)
#2 It's modded and upgeaded etc ending up with a machine that is still a compromise and cost twice the price of doing correct first time.
#3 It's frustrated the hell out of you to the point of giving up completley putting off CNC forever.

My advise is wait save up £1000-1200 minimum and do it correctly first time. In the mean time while saving plan and check out every thread then start your own thread asking about anything that your unsure about or can't find in other threads.
If you do this you'll get a nice reliable usable working machine much quicker than rushing in and frustrating the hell out of you.

Good luck.