Hi Neil, welcome to the forums.
Depends on how much you want to spend but I think the cheapest way is to go to somewhere like 7dayshop and get the Cokin holder and adaptor and then buy Kood P size filters.
Filter Holder is
here
Adaptor ring (67mm as I don't know what size you'd need) is
here
You can get Kood P size filters from
Hilton Photographic. It's a very simple set up but it'll cost you around £40 for the lot which is pretty cheap!