I am from Syrian and have permanent residence in Saudi Arabia and Permanent Visa to Canada to join my mom there. I am travelling to Canada via Etihad air flight. I have a stopover halt at London Heathrow Airport for 4 hours 45 minutes to board the connecting flight to Canada. I have a valid permanent visa to travel to Canada; I am unsure whether I will need a Transit visa for the UK. Please advise.
This should give you a better and more reliable answer: https://www.iatatravelcentre.com/
The airline should also be able to give you the information you seek, as they are liable if they send you without a visa if you actually need one.