I'm trying to fathom the precise wording on the upright sign:

1. TSM Chapter 3 (para 13.23.8) tells me I should omit the time period when the bay operates at all times. So, it would be "No waiting except police vehicles".
2. TSRGD (S4-2-4) tells me I "must include" a time period, which in this case is "at any time". So, it would be "No waiting at any time except police vehicles". And, indeed, the DfT Working Drawing P650.2 includes an example with this exact wording.

Another odd thing is the TSRGD describes the "No Waiting" symbol (S4-3-1) for use where waiting is "prohibited for a time that is not continuous throughout the year". Presumably because we don't erect signs for double-yellow lines ("no waiting at any time" that applies all year round). Well, what about "No waiting" for a police, taxi, or ambulance bay that IS continuous throughout the whole year?

There are a number of errors still in 2016 TSRGD (despite the 2017 corrections), and I think you've found another one. You're right that the description of S4-3-1 precludes the use of that row for anything that is continuous throughout the year. So you are left searching for another row in that table to use instead, but there isn't one (unless you change from 'no waiting' to 'no stopping').

So strictly speaking, I think you need to apply to DfT for authorisation. That would also have the benefit of alerting them to this error to add to their list. But for all practical purposes, following a current DfT working drawing is almost certainly OK and very unlikely to be challenged.

DfT might prefer to authorise it with "at any time" omitted, as that shows a greater distinction from S4-3-1 in TSRGD and thus greater justification for having the authorisation. But if you're not doing that, it's probably better to follow the WD (and be a bit closer to complying with TSRGD) by including the "at any time".