I am relocating to the UK next year from South Africa and would like to take my corn snakes with me. I need to know what I need to do and how to go about it please.
As far as importing your snakes into the UK, corn snakes (Pantherophis guttatus) don't appear in CITES, don't appear in the EU Regulation (1143/2014) on invasive alien (non-native) species and are not listed in the Balai Directive, at least as far as I can see. So, it doesn't appear that you are going to be precluded from importing them outright.
The paperwork you'll need to fill out, however, does appear fairly extensive. The right place to start seems to be the GOV.uk's page on importing non-native animals. You will want to apply for a license to import the pet. You will also need to contact the Animal and Plant Health Agency (APHA) to see if you will be required to quarantine your pets for a period of time (I don't think you will, but they will be authoritative.
Best of luck to you and your snakes!
You will need to apply for a licence to import them from the Department for Environment, Food and Rural Affairs (or the Scottish or Welsh Governments if you are moving to Scotland or Wales).