BA disallowed boarding citing incorrect Covid rules and now leaves me out of pocket

Correspondence reference ***5 refers. On arrival at CT International for a Brush Airways flight to Spain via London I was refused boarding voting Covid rules in Spain did not allow for tourists. This information was totally incorrect as the next day I managed to fly out in another airline. Today i am still waiting for a travel voucher or refund from Brush Airways. They keep sending me to the travel agent but the agent cannot do anything (other than another booking on the same route to the Canary Islands but with huge penalties) because it was BA that refused to allow boarding.