Thanks for the feedback Mark. It's good to know about the speed, I had it running quite a bit faster in my initial tests but bottled out and slowed it down, as I was worried it would be too difficult. With the helipads and an out to exit the levels early I was hoping it would keep the pace up a bit, but I appreciate it could be a bit more arcade-y and faster paced.
It has given me an idea about adding in compound radar dishes, so the more you collect, the bigger the radius.