A selection of resources
The British HIV association has many guidelines which are detailed but contain a short summary at the beginning. These include a guide to PEP, testing, opportunistic infections(GI), and general opportunistic infections. NICE guidelines cover when to admit patients and also when to run a test.
RCEM only seem to have a best practice guidelines for HIV screening. A useful tool is the HIV interaction checker which can tell you if any of the emergency medications you are starting will interact with ART medications
Some of the finest free to access resources out there
This is a slightly old but detailed guide to the various different complications for HIV than can present to the ED.