No disrespect to the poster - but power is one area you should NOT take shortcuts in.
You should not try to draw more than 10A from a 10A socket - especially in older homes, which may not have the correct circuit breakers/RCD etc.
The last thing you want to do is overload the circuit while you're away, and come back to a house and car reduced to a pile of ashes. It's not worth it - pay a licenced sparky to come and install the correct breaker, correct GPO, and ensure the thing is up to code.
We're spending 70k+ on these cars, we can surely afford to setup a proper charger/wiring/point that is safe to use and won't put your life/car/house at risk.