Matt, I managed my 2.5k swim (46min) last night needing only an additional 11minutes over my typical 1500 time 3 months ago (35min) and felt like I could have kept going and going. So yes, it definitely gets easier and faster. Not sure whether the drills, the reps or the consistency has made the difference but I suspect it's a combination of all three. Good luck in the parkrun.
Seren, I'm finding that the legs are the limiting factor rather than my ticker. Expect they'll toughen up a bit over the next few weeks