You can find out more information about Name.Co.UK here. The promo price of £1.99 is only valid for the first year registration of your .com, do not apply to renewals and transfers. Especially if you are new to Names.com.uk and your account is registered within the last 30 days, you will receive one .uk and one.co.uk domain that matched to your .com completely free.
No voucher code is needed, just click on the link below and grab your domain.
>>> Visit Name.Co.Uk and Register your .com for £1.99 right now
(*) Payment method: Credit or Debit Card. Renews for £23.99.
A note that Names.Co.Uk charges £5.99 for Domain Privacy service, so if you want to hide your domain information, you have to pay £7.98 in total.
Good luck 🙂