If existing law were enforced, they already could be sent to clink:
S 45 of the Serious Crime Act 2015, Offence of participating in activities of organised crime group
(1)A person who participates in the criminal activities of an organised crime group commits an offence.
(2)For this purpose, a person participates in the criminal activities of an organised crime group if the person takes part in any activities that the person knows or reasonably suspects—
(a)are criminal activities of an organised crime group, or
(b)will help an organised crime group to carry on criminal activities.
It's pretty clear that by paying a ransom, that helps and organised crime group to carry on their activity. The problem here is the lack of skill and determination on the part of the authorities, and a willingness to see corporate entities as victims of crime, rather than participants in a system of crime which (in most cases) they could have avoided by appropriate action beforehand. I'm sure many will disagree with me painting ransom-paying corporates as participants in crime, so let me be clear I think (eg) fraud or ransomware attacks against individuals are a totally different matter.