(Have just seen that someone else has posted but I haven't read it yet so apologies if I repeat what's already been said!
Hi there,
i am by no means an expert as I am new to veg growing this year too. I have just finished building my raised beds though so I have a few tips that I gathered from folk on here and books etc.
The cost of top soil was a suprise to me but in the end I did find somewhere who sold me a ton for 35 quid. The company name was Beatsons, I don't know if they are in you area too but worth a try. If not keep shopping around. Try freecycle and gumtree because there are often people trying to get rid of topsoil. Also landscape gardeners, builders etc, they often sell it for less money.
I dug soil up from my paths that run through my beds and forked it in to what was already there. This along with digging over the original soil really added height.
If you can get well rotted manure than you can add that in too, apparantly it does wonders. Don't add it to an area where you plan to grow carrots or parsnips though.They're not keen on the poo!
If you have lifted turf to make way for your beds then some people suggest turning it over and putting it in the bottom of the beds with newspaper over the top, then your soil etc. I didn't choose to do this in the end as it turned out I had enough to fill but it's something you could look into.
Finally, you may already know all of this so forgive me if you do, everyone I have asked says that the level of the soil will rise over time and therefore we shouldn't fill our beds right to the top.
Finally finally! ended up with a mix of topsoil (original), bought screened top soil and bought compost. Focus had a good deal on New Horizon compost that saved me alot of cash!
Hope I've been of some help!
Good luck