These are changing times, and a lot of surviving Met. material has gone with conductor rail renewals and line upgrades in recent times. I can think of some possibilities but it's always a case of checking to see if it survives. An example is conductor rail ramps, with the Met using several unique styles according to purpose. Ramps of one particular Met. type were removed with the layout changes made at Uxbridge last year.
My father and I looked out for these things and speculated whether each instance was a true Met survival. It really isn't possible to be certain without knowing what's been done to the track over the years. Having made a detour today, there is still a section of running line where there are short lengths of conductor rail that are extremely worn yet definitely of much lighter section - there are butt joints into much larger standard conductor rail. I'm confident that this rail has been there as long as I can remember, has survived the arrival of flat-bottom rail and some of this seemingly old rail is supported on the modern forms of insulator. It can only be a matter of time before it is replaced by the new rail, which is aluminium alloy section with a steel cap as rubbing surface. Note that the Met. used 100lb & 120lb sections compared to the LT 150lb.
An example of the effects of renewals comes up in this thread, post 234, showing loco 11 at Baker Street, late 1930s. The siding has a Met. buffer. By 1943 the siding was extended slightly with a concrete stop block. Around 1946, this in turn was replaced by a buffer to LT New Works standards of the time, when the siding was shortened again to make space in advance of major building works on the Baker Street site. So, easy to blink and miss the changes. There is a surviving Met. rail-built buffer, now derelict and unconnected, at the base of the former connection into Willesden Green yard, visible from [fast-moving] passing trains.