Small circuits and Small circuit wire?

I am new to the fiddling with wires stuff. Just about to dismantle a bluetooth headset and I notice that the wire inside is tiny!! I intend to lengthen the wire to the microphone and earpiece but my wire is nowhere near as thin.

Will it make the circuit run slower if I put thick wire on thin wire? 
If I need it, where can I get thin wire from in the UK? 
Also, is there a better nomenclature for thin wire or thick wire or have I nailed it?

Thanks in advance

AndyGadget6 years ago
Thick wire and thin wire sums it up nicely. There are ways of specifying exact thickness (either metric measurement of diameter or AWG - American Wire Gauge) but in your headset it is not at all critical - Anything will do as long as it is flexible enough to do the job.
The wire may well be enamelled coper wire which has a thin insulating coating on it.  If you're extending it, it may be easier to solder to the two points it links rather than trying to solder to the end it as it will be hard to solder to.