Hi @Deb117
Not entirely sure what you mean by an exemption code. You can use VAT Code Z=0% or Exempt for this.
You may need a Commodity Code for each line item (see https://www.gov.uk/trade-tariff) but to/from Channel Islands I don't think will be too much of an issue.
You will need to keep some proof of export - shipping documents or bill of lading - in case HMRC checks up.
For information on VAT on goods exported from the UK, read through VAT Notice 703 : https://www.gov.uk/guidance/vat-on-goods-exported-from-the-uk-notice-703
In particular, section 2.7 Countries that are part of the UK for VAT purposes...
The Channel Islands are not part of the UK for fiscal (VAT) purposes. Supplies of goods sent to the Channel Islands are regarded as exports for VAT purposes and may be zero-rated if the conditions set out in paragraph 3.3 or 3.4 are met. See paragraph 7.12 for information about evidence of export of goods to the Channel Islands.
Hope this helps.