There are several places in the UK where you can find custom boxes at wholesale prices:

1. Packaging Chimp (www.packagingchimp.co.uk)
2. Wholesale Packaging (www.wholesalepackaging.co.uk)
3. Davpack (www.davpack.co.uk)
4. Rajapack (www.rajapack.co.uk)
5. Packaging2Buy (www.packaging2buy.co.uk)

Make sure to compare prices and specifications to find the best option for your needs.