depends on how much you want to spend, do you want to return it to stock, or to improve it slightly.
Option 1
Original bumper glued, grille cut out, replace with some grille mesh. £100-£150
Option 2
get a 2nd hand front bumper £150 - £200 but if it needs respraying to match the car then add another £250-£450
Option 3
buy after market bumper, still needs to be sprayed could be anywhere between £600-£2000 depending on what bumper you went for and how much prep work it needed. etc