It’s easy. W is a vowel in Welsh. It sounds similar to ö in German and it can be modified as ŵ to elongate the sound such as in the word dŵr which means water.
Wrwgwai or Wcrain (for example) are the natural way to spell those countries using the Welsh alphabet. Its a highly phonetic language believe it or not.
There are services in the UK where they come and clear the house for free. They take the risk on the value of what is in there.