HMRC have issued guidance on the tax treatment of payments to individuals and other non-corporates following share capital reduction.
In brief, a repayment of share capital, including premium, following such a reduction is not a distribution and so is not chargeable to income tax.
There may, however, be a charge to capital gains tax as a capital distribution.
If share capital, including premium, is reduced and a reserve is created and treated as a realised profit that treatment will be applied for tax purposes and a payment out of the realised profit will be chargeable to income tax.