One question - will the raised beds be sited over existing soil, or onto a solid surface like concrete?

Before you use the railway sleepers you need to make sure what type you have. All used sleepers have been treated with preservatives, you can't use a creosote treated one for fruit that you will use for example.

My railway sleepers are extremely heavy so if you are piling them up and filling with soil etc - you might want to make sure there are no old drains underneath that could collapse under the weight?

thank you for your help and will probably use scaffolding planks. I will be building on to concrete, leaving space at the bottom to allow drainage to the existing drains

Then you've a problem with growing fruit trees or anything over about 4 feet - these things will need to go right down into the soil, so unless you make your raised beds 6 feet or more deep, which is hardly practical, you'll not be able to grow larger plants. Is there no way you can remove the concrete in the appropriate areas and build your beds on open soil?

thanks bamboo ,the concrete is very thick but i could persevere at the area where i would like to plant my tree many thanks