You must make sure you get them right.
Use the UK Trade Tariff to check you have the right code for export (you should also use these for import declarations).
You can find your local chamber details and the training/international trade support they offer. They can help you with queries about export documentation for shipments to the EU and ROW and also offer a customs declaration service.
Visit their website and find your local international trade adviser.
They have also launched some videos and offer a variety of support. Some regions have launched the Export Academy which is a series of 10 free training sessions for small businesses with a turnover below 拢500k.
Your local business growth hub may have a list of other support/funding available.