Hello Allan, like you we live in a converted barn with thick walls and heavily beamed ceilings, we couldn’t receive Wi-Fi in our sitting room, we have used TP link which we bought from Curry’s, we have used the existing set for about 6 years, the only issue we find is that they need to be re- paired (not repaired), I can’t tell you how much we paid for them as to long ago, maybe there are other things available but if the need arose again we would buy TP Link.

Good luck hope the above helps.