Light signals controlling traffic
Flashing red lights
1 signal, in the order the Highway Code lists them. Each one has a page of its own, so you can link to a single signal.
Every one, in the order the Code lists them
What the Highway Code says about this group
At level crossings, lifting bridges, airfields, fire stations, etc.
The rest of light signals controlling traffic
3 more groupsOne search covers the whole Code and the whole library
Nobody looking something up knows whether the answer is a rule or a signal, so there is one field for both, and neither needs an account.