A ton is reckoned to be a cubic metre which is 1,000 litres. I think.

If your raised beds are sitting on concrete slabs how is the rain going to drain through?

thank you Owdboggy, that makes sense. x
Moongrowe i hadn't considered that yet! I guess a gravel base to start then splice the side of the liner.
Got any tips, i can see a boggy dingy mess in my minds eye.
The reason they're going to be on slabs is because they will be left there after moving a large shed that is there at the moment. Perhaps if i remove one or two for each bed that will help.

It would be better if you removed the paving slabs.

Yup remove all the slabs!

If you don't want the work involved why not offer them on Freecycle with the condition that the person who wants them takes them up? There is usually a high demand for free slabs.

Out of curiousity how do you know you need 1040ltrs of soil for this project?,While 1 ton is 1000ltrs ,1 cubic metre
will be more like 2 tons of soil,even more confusing the bulk bags of soil are usually a bit less than a ton but it can vary greatly depending on water content,a cubic metre of concrete usually comes in at nearer 2.5 tons which shows volume to weight is dependant on the material and not a simple calculation.

Im getting mixed up now ! meant to write 1 cubic metre (not 1 ton)is 1000ltrs the rest is correct (i think!).

Be careful buying top soil. These are usually builders who steal the top soil scraped from levelled off house building sites on a Sunday afternoon using the firm's fork lift diggers, leaving the new owners with sub-standard soil. This is the reason I have to contend with sub-standard clay soil. No amount of manure/soil improvers ever makes up the loss. They use the firms lorry and charge £100 a load. I have known these thieves steal stacked top soil from allotments where pipework was being replaced. It will be expensive buying it in bags. Maybe cheap Multipurpose Compost would be a better option on top of the base soil you already have. Vegetables only need about 10" depth of nutritious soil, some less than that.