With regards to price it varies between import and export also the amount of commodity codes on the transaction. Obviously the amount of complexity to the declaration such as more commodity codes will cost more money as more admin will be needed, same for importing as there is more documentation needed and more personnel hours to go into completing the customs declaration. Please note if a customs declaration is required but then gets cancelled after submitting an admin charge will be billed.
Export Declaration £50 for 3 commodity codes then £5 per each commodity code thereafter.
Import Declaration £75 for 3 commodity codes then £5 per each commodity code thereafter.