There are so many great places to get advice, and Garden Organic has a great set of guidelines to help.
From personal experience, I used Earth Cycle Top Soil Supreme to prepare the soil for lawn seed. From previous posts you will see that the garden bloomed! When we had to lay some stepping stones to our shed, the soil was unrecognisable from the start of the makeover. There were so many worms, a sign of healthy soil!
Also, join Garden Organic's 'I don't Dig Peat' campaign to get gardeners to stop using peat in their gardens. Earth Cycle massively supports this campaign. Look at the ingredients of the compost you are buying, especially Multi-purpose composts, which still have large amounts of peat in them. It may seem like a simple and small thing to do, but if gardeners stop using peat, it can make a huge difference to the environment.