After inspection of my stock intercooler, which had a large amount of gloopy oil in it I'm thinking maybe I can get a larger one to do a more efficient job.

I appreciate that landrover spent a lot on this stock intercooler.

The one on my car had taken a bit of a ding

judging by observing live readings of the air intake temps,
i put forward that for uk ambient temps, the stock size intercooler does the job well enough.
in theory, a larger intercooler might cause some turbo lag.