Last week I took the opportunity of having the mains power off to test the RCBOs in a Wylex Consumer Unit, fitted nearly 5 years ago, which has the following:
1 off NHXS1B40, 4 off NHXS1B32, 2 off NHXS1B16, 3 off NHXS1B06 and 1 off NHXS1B25
Now on Test, the B40 switch went to the mid position...