Best rope for anchors is Octoplait, but it normally costs a fortune. However, buy mail order from this guy: firstname.lastname@example.org
at loads less than retail.
or look on Ebay - he trades as: The_Rigging_Loft
My 12mm octoplait came in at £1.50 per metre and he does all sorts of different rope. I also bought floating line (to use for stern lines) from him at 75p per metre.
I have 60m of 12mm Octoplait and 10m chain on a 7.5kg anchor but you won't need anything like that! It's suitable for a boat up to 10m anchoring in a depth of up to 15m. As long as you've got a few metres of chain on the anchor you should be OK.