Just had a quote from those guys, ~£4,500, they are aware of the CRL/Alpha situation...Sennocke are who you get when you go through Buildzone/SelfBuild Zone.
I initiated a dispute with Barclaycard over this payment so let's see what they come back with. They were very helpful.
On the Alpha Insurance websiteto claim the premium back it says (https://alphagroup.dk/1647-2/):
"Generally the Danish Guarantee Fund does not cover premium refunds on the following insurance types:
British taxi insurances
British insurances on buildings"