Chances are your splitter is HDCP 1.4 and your Sky Q will want HDCP 2.2 if connected to a UHD display. If it's connected to an HD display it will be fine with HDCP 1.4. I expect.
I suspect my current splitter is HDCP 1.4, but feeds well to my UHD TV from a Sky+HD box.
Sky+HD will be HDCP 1.4 max - so won't have an issue. Most (but not all early) UHD TVs are HDCP 2.2 - which is backwards compatible with HDCP 1.4. HD TVs will be HDCP 1.4 max.
An HD source will be HDCP 1.4 so will work fine into an HDCP 1.4 HD display, or an HDCP 2.2 display running in backwards compatibility mode.
A UHD source will be HDCP 2.2 UHD into a UHD TV with an HDCP 2.2 input, and will drop down to HDCP 1.4 HD to feed an HDCP 1.4 HD display.
What most UHD sources will complain about is feeding a UHD signal to a UHD display in HDCP 1.4. You'll probably get an error complaining about the lack of HDCP 2.2 support.
A quick search has just found a reasonably priced similar splitter which offers HDCP 2.2 for up to UHD quality.
However remember some UHD modes are HDMI 1.4 compatible - so you may find you have something that is HDCP 2.2 but not HDMI 2.0 compatible.