You dont really need shoes for a newborn cause for one they arnt exactly doing any walking and also cause it restricts their foot movement, if you want something to keep their feet warm when your out then just opt for little soft pram booties, they should be made entirly from soft fabric or soft leather NEVER with hard soles. Like Layla said mothercare are very good for them at a very good price. Even once they start crawling or cruzing never go for hard soles as this will hinder their development, only get hard soled shoes once they have been properly walking by themselves for 6 weeks.
Some trendy shops like Next do little trainers and stuff for babies that are designed like adult trainers but these are really bad for babies feet and should never be used, and can result in collapsed arches, inward turning feet and slow down your child development as they dont allow them to move their feet properly and are far to heavy, so avoid anything like this at all costs.