Well all 3 of the bikes you're looking at are great starter bikes, and also excellent for the money. If I were you I would definately splash out that little bit more than £500 and go for the comp. As for getting a 20 or 26" bike (Mod or Stock), it all really depends on what you are more suited too. Ofcourse height and weight make a difference too but it's really just your personal prefence. Oh, and when you do make a choice on what bike you want, Buy it from this website: http://www.tartybikes.co.uk Hope i've helped out