Hi one_knot - I did mine at Bristol which is a pretty busy international airport and didn't really find it helped. You're not in the airport environment that much and by the time you're in the aircraft you'll be doing upper air work in the local practice area and flying routes. Your workload there will be more a function of the airways structure rather than the size of the airfield you departed from. It will be busier for you in the final stages of your approaches for sure, but I found a busy airport a problem as through the 16 hours of flying I did I wasted around an hour in total orbiting while queues of jet traffic landed ahead of us. At GBP6 per minute that is a lot of money to waste.
By the time you get to the IR you should be good at RT anyway so I'm not sure how much extra you'll learn.