Hi again Phil,
Are you and I living in a parallel universe as well as the same city?
I have to agree with Will on this one - removing the fuel tank is a right pain. I'm sure by now you agree as well.
Considering how easy it looks, it can take some effort and I ended up manhandling mine out.
It's possible to get your tank out alone, but you'll find that the aid of a friend for five minutes will make it much easier. One can manoeuvre and hold the tank in place while the other lifts/pushes.
To start with, try sliding the rubber boot right down filler neck to the top of the tank. It's probably not a bad idea to leave the fuel sender assembly in the tank to prevent crud falling in and contaminating the tank.
My tank also jammed when I was trying to get it out. For some reason that I don't understand, these things just don't come through the hole easily. Unfortunately, I was alone at the time and didn't have my tools so my technique of removing the tank was born out of using what was handy at the time (mixed with impatience),more than it was from well measured and carefully considered problem solving.
I ended up sliding underneath and pushing the tank upwards. When the tank was about halfway out it jammed solid, just as you've experienced. Oddly the lower walls of the tank were seemingly wider than the hole. Not by much, but enough to still cause a good solid jam.
I didn't want to hit it with a rubber mallet and risk denting a pristine tank, so I got a short length of timber that I propped vertically underneath the tank, then I simply pushed down hard on the body of the car and that pushed the tank through the hole surprisingly easy.
The length of timber was an inch or two longer than the height of the tank from the ground, which lifted the car slightly on it's suspension and made the task of pushing down easier as gravity worked in my favour.
Being paranoid of denting the tank, I protected it by nailing a broad piece of plywood to the top of the piece of timber to spread the pressure on surface of the tank.
If I'd had a trolley jack handy at the time, I probably would have used that instead, but I didn't. Similarly, if I'd had someone to help this would definitlely have been easier and possibly unnecessary, but again I didn't. But it worked and my tank is still straight
As for the spark issue, caution is always best.
Jay makes some good points, but in the end you're the one with your head in the boot with the tank, so take whatever precautions make you feel comfortable.
No-one will call you a fool for NOT setting yourself or your car on fire!
However I will be first in line to offer to buy your cache of parts if you set your 105 alight
Interestingly though, I saw an episode of Myth Busters where they were throwing lit cigarettes into pools of petrol to see if they could start a fire like you see in the movies. They weren't able to achieve ignition at all with a cigarette. They needed an actual open flame like that from a lighter or a burning piece of paper to get the petrol to ignite. But still, I don't think you can be too careful.