Weed suppressant fabric

That's quite a lot of fabric - you could consider green manure or simply leaving it fallow if you wanted (will need to keep an eye on the weeds).  Another alternative is cardboard (e.g. if you have any bike shops near you).

If you want to use fabric, go for a woven variety rather than one which is completely impermeable.  The wider the better; it means there's fewer edges for the wind to get under and to keep pinned down (you can use bricks, or large milk bottles filled with water, as well as the wire pins you can buy).

Online retailers / ebay will be cheapest but it still won't be cheap, I should think.  If it's only for this season then you don't need to go for the most expensive.  The heavier duty, the more expensive.

I would leave the soil open for the winter, particularly if the land is heavy, as the frost will do it a lot of good.

Planting a green manure is another option - that will help lock in the nutrients, there are types that are good for over winter on heavy land too (such as Field Beans).

Come next Spring (after you have dug in any green manure ) covering with a black weed suppressing membrane will act as a mulch to lock in moisture, and capture the sun's heat, plus keep the weeds down all summer (i.e. you plant "through" X-slits in the membrane).  If you are thoughtful about where you cut holes for the plants, and organised enough to keep it from year to year - labelled so you know which piece has which hole spacing  - then it will last for years, particularly if you buy a thicker / heavier duty membrane.  "Heavy duty" starts at, say, 100 gsm - higher numbers are thicker, but I would expect even 80 gsm to last several years.

As others have said only get the woven type, and make sure it is UV stabilised (some is designed to be covered by ornamental bark etc. which means it is not in the sun and thus won't have the same protection)

I dig in manure and leave it for the winter - nothing much will grow but the worms will do wonders with teh manure. 

When I got my plot it was in terrible state and I hd intended on using weed suppressant sheeting. After researching around here I went and bought a roll of mylex which seems to be one of the best. But I never used it in the way I'd planned, as by the time came I'd caught plot-itis and set to digging/clearing/hoeing. But the mylex has been useful, have planted a couple of strawberry beds through it with the near elimination of all weeds. Only problem it frays when you cut holes through. But its porous so the ground does not dry up and should last years.

When I got my plot it was in terrible state and I hd intended on using weed suppressant sheeting. After researching around here I went and bought a roll of mylex which seems to be one of the best. But I never used it in the way I'd planned, as by the time came I'd caught plot-itis and set to digging/clearing/hoeing. But the mylex has been useful, have planted a couple of strawberry beds through it with the near elimination of all weeds. Only problem it frays when you cut holes through. But its porous so the ground does not dry up and should last years.

About that problem with it fraying - I was thinking about this today and remembered I'd seen a post or website somewhere where  someone used a blowlamp to burn holes in it, rather than cutting (like I've done too).

Presumably this would seal the edges and stop fraying? I'm going to try that myself soon (for planting out my autumn garlic) and if it works, I'm going to run the blowlamp along the cut edges to seal them too - it's a pain constantly clearing the threads from the end of my strimmer.