Steveco
I assume that you know that the DPI figure is meaningless in a digital image. Its like me saying I have 100,000 in my account and not letting you know if I have Euro, South Korean Won or Japanese Yen
what matters is pixels, and 1800 is not much as you know. Loris is on to something which is important, that is to
tell them you want the scans made for big prints
Personally I would recommend you ask point blank "
do you have a noritsu mini lab?"
if the answer is no, then move on. I've had some
fantastic results from Noritsu minilabs (link is to my blog). I asked for scans and developing and asked the person what density they scan at. They were confused (of course) and asked me "did I want scans for large prints?" I said yes, and got essentially 6Megapixel scans.