Hi Steve,
Fuel prices are generated by the FlyNET database as and when airports are added. All VA's pay the same price for fuel at each of the airports.
No Bristol Britannia as we are still waiting for a suitable quality model for FS.
No Concorde until fare structures allow 'premium' fares to be chosen for certain aircraft types. All FlyNET fares are 'economy' fares and make the Concorde a big loss maker on FlyNET - it's been tried. Similarly exec jet operations are also in a similar position until realistic fares can be applied. It's on the 'wish list' at FlyNET.
The url for your signature as well as your signature is displayed at the bottom of your profile page at FlyNET. Use the url to attach a sig through your profile on CBFS forums. Your particular url is
http://flynet.en-studios.de/signatures/CBF117.png by putting

after the url it will display as your signature.
You can change your default sig pic aircraft through your profile page. If you make a flight booking then the sig pic aircraft will change to the booked type.
Rgds
John