Never been to LHR. Is it really worse than Turkey? In IST you can easily need to walk 25 minutes. They put the TLV flight at the farthest gate. Literally the last gate.
I haven't been to LHR in quite a long while. I don't recall long walks, but I do recall long bus rides for connections.
TLV and US gates at IST are YMMV, I've had them all the way at the end (last time I connected, were they not only both all the way at the end, but both required bus rides to the aircraft
), and I've had them both right in the center, with the shortest possible walk to/from the lounge. All of this should change after March 1st (though I wouldn't hold my breath, as the date has been pushed off a couple of times).
YYZ is quite bad with walking distances.