I appreciate that Errol is very close to Dundee and so that is why the drop aircraft uses that frequency.
Would it not however make more sense to use Leuchars? They have radar - which as I understand it, Dundee do not. Leuchars are the service that most aircraft will use when transiting the area. Getting a traffic service from Leuchars is much more likely to address these matters than talking to Dundee - who mostly will not know what is happening in the area apart from their own inbounds.
If nothing else hearing a paradropping aircraft on the frequency is going to get most peoples' attention.