Attaching Load to Source on Mosfet
Would I be correct in thinking that using a P-channel mosfet would
  serve my purpose?


Yes, you would be absolutely right.

Since MOSFET's are turned on by applying a voltage between Source and Gate, the diode in your second image acts as that very voltage drop that is stolen from your Source-Gate potential. That pretty much means, that the transistor is no longer turned on by the full battery voltage, but rather \$V_{bat}-V_{diode}\$.

What you are looking for is what's called a high-side switch. This usually requires a P-channel MOSFET.







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