I have a new greenhouse sited over a former raspberry bed. I have read that it is preferable to grow tomatoes, cucumbers, peppers etc in pots, however for the first year would it be okay to grow straight into the greenhouse soil?
You don't say where in the country you are based: different areas have differing types of soil. If the plot has grown raspberries before you should be OK with tomatoes & peppers in the same greenhouse as they are both of the solanum family. Cucumbers in the same greenhouse as Toms is not recommended by many gardeners (though I have to say I have grown cucumbers in my g/house alongside toms for past 2 years with reasonable results). Growing in the soil should be OK for the first year but be aware that after that grow-bags/pots etc will be needed as the soil can accumulate pests & diseases if the same type of plants are grown in the soil year on year but it would be OK if you replace all the GH soil each year and properly clean & disinfect the GH with Jeyes Fluid (or similar) every year whichever style of growing you adopt.