Around where I live, courts decide differently based on the nature of the enterprise. If a company gets an invoice and pays up, they basically agreed to the charge. That's because companies are expected to understand and check invoices. For private individuals, if they pay an invoice and only later realize that they didn't in fact wanted to pay, the contract that came into being based on their payment can be annulled. And in some cases it leads to charges of fraud. That's not to say that companies can't be illegally defrauded, just that the bars are higher.
In the .uk case, this means companies would have to make sure they didn't pay. But consumers could in fact claim they were tricked and demand restitution even after paying. I don't know how such cases are handled in the UK however.
In any case: Transfer your .co.uk to a reputable registrar. Don't do business with outfits who pull shit like this.