Please call!!
Having worked at a couple of radar units, I've seen first hand the havoc that results from someone blithely passing by not talking to anyone. That's not great when a 737 is just about to establish on the localiser and I'm watching someone out the window blatting through the final approach at 3 miles.
Traffic on a deconfliction service has to separated from "unknowns" by 5 miles or 3000ft. If a contact appears on the screen as primary only, 5 miles lateral separation must be applied against DS traffic. That's a lot of vectoring and hard work, and I'm not even mentioning what else might be going on - other traffic, potential conflictions, pop-ups, co-ordination etc etc.
I've said it before but I'm going to re-iterate: Just because it's legal (yes, you can overfly an airfield at 2100ft without talking to them) doesn't mean it's safe or sensible.
Before I go, one or two more points.
Box two. Use it! It may just be useful one day
Never assume, check. For example, those nice shiny charts issued every March might not be correct. The ones issued this year don't show the IAP arrows at Newquay. Well, we have IAPs.