ask your friendly local plumb center
15mm is 1/2" BSP and 22mm is 3/4" BSP
Always find them over priced, Plumb Center IMO has always been expensive B&Q can be cheaper than them
Sorry but that isn't true, 15mm is slightly bigger than 1/2 inch and 22mm is shorter than 1 inch, and you would need to use the likes of this for the 15mm Yorkshire Kuterlite Straight Tap Connector 626 15mm x ½" - Screwfix.com, Where the Trade Buys
And this Yorkshire Kuterlite Straight Tap Connector 626 22mm x ¾" - Screwfix.com, Where the Trade Buys for the 22mm.
And screwfix / and mainly toolstation now are cheaper than both of them.