Actually, the great big ones you see most people play ARE 3/4 size! I've never actually seen a full-size bass, but hear that they have their own gravity...
You can get a decent beginner's bass for a few hundred quid, or, if you are lucky, sometimes people give 'em away in Scoop etc ("Free to a good home"

.
I'll try and find someone dedicated for lessons, but if you're stuck then I can get you started...
Sam
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Hello, my name is Sam Bates. I play, produce and promote music. If you would like to gorge on me-related info, here is some stuff I do:
www.myspace.com/matthewkilford
www.myspace.com/ratsruinedmybrain
www.playdead events.co.uk
Competetive rates for live and studio sound engineering. Mixing, mastering and production contracts all considered. PM me!