Sorry that you're not getting the speeds you'd expect with your wireless connection.
As Chenks has said, WiFi isn't always reliable due to many factors that can affect it. You can find more information about getting the best out of your wireless connection via this link here.
I'm glad you're getting the expected wired speeds and this connection is performing well.
You could potentially be affected by congestion in your area at the moment, however the speeds you're getting on a wired connection suggests a low impact to your property. The fault reference for this is F007346980 and you can give this to any agent you speak to for an update.
You should be eligible for a service credit due to this, so I'll send you a private message now to clear account security.