I ended up using a 25mm flat wood drill bit. Created a hole snug enough for the thread of the tap to screw into. I put the washer on the inside, but it leaked a bit so thinking it should go on the outside. Will try that next time.
Found the Brewferm bottling wand a bit slower than the Coopers one, although it was nice having a tap right at the bottom of the bucket, rather than About 10cm up like the Coopers one is. So from now on fermenting in the Coopers as I like the krausen ring and the tap for taking samples then syphon off into my new bottling bucket.