I noted that the 1 year option was becoming available
Heart Internet had not applied this, this morning, so sent them a Support Ticket
I was advised it was not yet activated, but would be between 08:00 and 11:00
It is now live
1 year is £3.99 plus VAT (£4.79)
2 years remains at £5.88 plus VAT (£7.06)
3 years is £8.97 plus VAT (£10.77)
4 years is £11.96 plus VAT (£14.35)
6 years is £17.94 plus VAT (£20.88)
The three years appears to be an error, as it should be 1.5 times two years...
The same issue occurs with 4 years
However, 6 years appears to have a (small) discount
and the same continues throughout as can be seen when doubling the price for two years to four years
Surely more years should be cheaper...
Don't even try to work out how they come to the price for 6 years (as it is neither 3 times two years nor 2 times three years)
Given Nominet charge a flat fee (of £2.50 per year) for each additional year from 3 years onwards, yet another con from Heart Internet

