Rock Sliders as sill for Disco 1

I know this has been done to death a little, but as I've a sill missing (well ok eaten by the rust monster), is it worth replacing both sills with rock sliders or just fixing the problem (repair one side) and looking at sliders to bolting onto the chassis?

Also, as I can't weld for toffee, any recommendations for welding near Bodmin Moor?

get a length of 60/30 or 60/40 box section and cut away the old sill. then drill a series of diagonally opposed holes in the floor of the disco, about 6mm should be fine. Offer up the box section and then weld thru the previously drilled holes. You don't need to be a good welder to do this, as long as you get good penetration If you're not happy with welding the brackets posts etc, to the box section get someone else to do it for you. But by doing the box section yourself, you'll have done all the hard work. And saved yourself a huge portion of the welding bill.