So I topped off the tank and was doing some final messing around with some ties/brackets for the gearbox cables and I notice a very strong smell of gas.
First things first - turn off the heater!
Second look under the car to find a puddle of gas :(
Looks like whomever did the welding on the filler didn't do such a great job and it has a hole or 5. It didn't show up before as wasn't under static pressure.
Off to find someone who can MIG weld aluminum