From Longman Dictionary of Contemporary Englishgo down a treatgo down a treatBritish English informalLIKE somebody OR something if something goes down a treat, people like it very much That new vegetarian restaurant seems to be going down a treat. → treat
Examples from the Corpus
go down a treat• It seems to be going down a treat.• It went down a treat with the matrons in safe seats like South-west Surrey. 