I'm looking to book a redemption flight (to MRU) and am going through different options - flying direct from LGW, starting from EDI and transiting through LGW, and starting in EDI with stopover in LGW.

I notice the taxes and charges are different for each - there's not a huge difference, but I'd be interested if anyone can actually explain them.

The differences are as follows (all prices are per adult):

Direct LGW-MRU

Passenger Service Charge: £12.27
Air Passenger Duty: £170.00
Fuel Surcharge: £359.00

EDI-LGW-MRU (no stopover)

Passenger Service Charge: £29.99
Air Passenger Duty: £170.00
Fuel Surcharge: £396.00

EDI-LGW-MRU (with stopover)

Passenger Service Charge: £29.99
Air Passenger Duty: £183.00
Fuel Surcharge: £396.00

To me, it looks like the differences are:

• Passenger Service Charges increases from £12.27 to £29.99 when both EDI and LGW are utilized. Do we pay the Passenger Service Charge for each UK airport we use on any one booking? It seems funny that adding EDI brings it up to exactly £29.99.
  
  
• Air Passenger Duty rises from £170 to £183 when adding a stopover. I presume this is because each flight is rated individually and this is the total (£13 is the surcharge on an EDI-LGW)
  
  
• Fuel Surcharge rises from £359 to £396 when adding EDI-LGW leg. Is this normal?

The price won't be the determining factor in what I book, but I'm interested in whether anyone can explain the differences.