Do I need eave protectors?

southcoastrgi

Furts, what you are suggesting is correct for a modern house that they try & seal up tighter than clingfilm, but for the OP's house it is totally overkill, clear any of the insulation away from the plate & the OP will have more than enough ventilation without spending a penny

cyclonebri1

But I do think that if there is a ventilation problem and the staining sounds to me like the existing bitumen felt weeping on the fascia, (however little of it there is left), then action needs to be taken. Clearing the eaves of course has to be done, but, on it's own it is unlikely to effect a cure.

2 points, absolutely ensure the loft insulation is maxed out, 50's houses didn't have much originally. This may however make the problem worse as the loft air will be cooler and release it's water content more easily.

What the roof does need IFthere is a condensation, is high level ventilation to give the warmer air that holds the most moisture a quick exit.

Money would be better spent on 4 roof vents, continuous ridge vent would be.
too expensive.

Some big if's of course, the op needs to determine the actual problem before spending money ;)