I am traveling YYZ - BOM via LHR. After Oct 14, 9W is scheduled to move to T4 and AC operates out of T3. BAA's website states that trains between Heathrow Central and T4 run every 15 minutes and it is a 3 minute ride. I wanted to know how reliable the service is and if I might experience any lengthy delays. The time between my connections is an hour and a half. I am hoping this should be enough for making the connection.
Any information/tip is appreciated.