Heathrow

www.trackmaps.co.uk/book5.htm

I think will have it covered

There has also been a detailed track map on this Forum in the past..perhaps some kind sould can point to the thread?

Terminal 5
Scissors crossover in the terminal sidings, on the west side of the station.

Terminal 123
Crossover and junction to the west of the station, comprising from west to east:

• Facing crossover between EB line from Terminal 4 and WB line from T123. The track before the building of PiccEx used to split so trains from T4 could access either platform at T123.
  
• Converging junction from T5, normally set T5 - T123
  

The WB line to T5 goes underneath the T4 loop.

Scissors crossover to the east of the station (this was the original set of crossover, before T4 was built).

Hatton Cross
Junction on the west, set for the T4 loop, trains on the 'old' formation to T123 get arbour and junction points reversed, pair of crossovers on east side (NOT a scissors), arranged as two separate crossovers training then facing as you proceed eastwards.

The various extensions towards and within Heathrow are quite interesting from a signalling design point of view, as you have almost all the possible layouts for a two track terminus using 4 sets of points:

Scissors in siding
Scissors on approach side
separate crossovers in sidings
separate crossovers in approach side

Each of these designs have their pros/cons; the only one that does not yet exist is the separate crossovers in the sidings option, however I'm pretty sure that exists elsewhere - perhaps in the undercroft at Manchester Piccadilly station, but it has been so long since I've looked at that installation, I wouldn't like to make a call.