The stock bolts should be replaced when replacing the wishbones.
These replacement M12 bolts are cheaper than the factory items at £1.80 each ref RYG10048 which retail at £3.85 each plus vat. 
A set of 4 will cost you £7.20 plus vat postage and packing in the UK is £4.20
Picture shows 4 old bolts removed.
Also consider the long bolt conversion if changing to poly bushes these require the captive nuts drilling through with a 12mm dia drill , the advantage of this conversion is that does not require the subframe dropping to remove the wishbones as the bolt is removed from the front.