Does a Philippine passport holder, based in UK need Transit Visa to lay over flight either Bucharest or Istanbul destination is Cairo Egypt?
For Bucharest a visa is not required, you can Transit Without a Visa:
TWOV (Transit Without Visa): Visa required, except for Passengers with a confirmed onward ticket for a flight to a third country within 24 hours. They must stay in the international transit area of the airport and have documents required for the next destination.
All the same conditions apply to Istanbul.
From Timatic (the database used by airlines).
Other conditions where you are visa exempt can be viewed here.