<p>I've just printed my very first part and it did not want to come loose from the build plate, it fact, it just broke instead.</p>

<p>I can heat the bed up again and work it off, but I wondered if a release agent would be better?</p>

<p>I have a silicon release spray (like those use with molds).  Could I spray the base with that before starting printing?</p>

PLA should not be printed at 235 °C. If your printer requires such high temperatures to make the filament very fluid, you have too much friction in your system, e.g. this can be caused by clogs or too low layer height printing the first few layers. Note that such high temperatures are also a cause for obstructions as the filament can carbonise creating clogs. On the other side, too low temperatures also cause too much friction or resistance.
The sound you are hearing is often referred to as "clicking" and can be caused by steps being missed or the extruder hobbed gear to skip back as a result of the friction/resistance.
Now that clicking is introduced, please look into
this answer
and
this answer
to answer your problem.