What sort of posts did you have? if they were concreted in wooden posts which have snapped, You can buy "metpost repair spurs" which are iron spikes designed to be bashed in at the edg of the old post (the repair ones have a right-angled spike, the regular spikes are a cross shaped spike to go into plain unconcreted earth). Metposts cost about £8-12 each depending on size. They are sold at homebase, b&q and Wickes (and probably elsewhere too).
Buy 2.1m (seven foot posts) for a six foot panel fence so that the posts are a bit taller. A good sledgehammer will cost you £25.
The best panels we've found are from waltons fencing because their basic six foot panels are about £18 (less if you buy bulk) and they do free delivery to most of the Uk.
and if you want them painted you can get big tub of fence preserver from Wilco's for a tenner.
B&Q sell some great metal fencing clips for £1 each that let you screw the panels diectly to the posts (no need for lifting like with simple c shaped fixings) you need four for each panel. Get the 47 mm size cos the smaller 35mm ones only do trellissing. It also means if a panel goes in future you can just take it out by removing eight screws.
So five panels would cost you about £80, seven posts at £12 each from Wickes are £84, seven metposts about £60, sledgehammer £25, a bag of screws £5, twenty posh b&q clips £20. Total - £274 if you are buying the new lumphammer.
Can you tell I've replaced a fence recently :)