If you're willing to spend a few quid, then I'd say Neil is spot on with the Irwin saw. As he says, cuts on the pull stroke, don't force it, let the saw do the work, if you are fairly intuitive you'll get a good idea fairly quickly. Don't drag it let the teeth work, they will be very sharp new and put no pressure on the push stroke. Just guide the saw. If you feel it gripping or the sound changes you're working it too hard. Might sound daft but I find if I remember to breathe regularly it helps slow me down, sounds daft but it's a good measure of concentration. You're looking for relaxed and fluid. Fast and Furious will do you no favours. Bit like a Vin Diesel movie you might need a few attempts. Might still turn out a bit rubbish 6 times down the line. 
I wouldn't buy a vice at this stage.
If you have a little scrap wood I'd improvise a type of bench hook. You can make a servicable 'clamp' that will serve just by screwing some larger bits of wood to the top plane/part and fit your Bobbin inside if you think outside the box. Wont grip like a vice but it will be enough to get away with it. All you need is enough to stop it moving about while you work. Really you just need to stop it rolling away. You just made your first Jig.
https://en.wikipedia.org/wiki/Bench_hook
Crack on. We want photos next.
I wouldn't buy a vice at this stage.
If you have a little scrap wood I'd improvise a type of bench hook. You can make a servicable 'clamp' that will serve just by screwing some larger bits of wood to the top plane/part and fit your Bobbin inside if you think outside the box. Wont grip like a vice but it will be enough to get away with it. All you need is enough to stop it moving about while you work. Really you just need to stop it rolling away. You just made your first Jig.
https://en.wikipedia.org/wiki/Bench_hook
Crack on. We want photos next.
