Well thanks to all for the pointers. I beat endless survival and made it through 44 waves of insanity before dying.
The build I used consisted of two cob cannons, a dozen frozen melon catapults, six fume shrooms and eight gloom shrooms, a couple cattails, spike rocks and about seven thousand sun points at the peak of the build which was around wave 23 or so. From there it was just a matter of holding on through forty waves, replanting where able and maintaining pumpkins on the gloom shrooms and sun producing plants. Two gloom shrooms in row two, one on each side of the pool were key to seriously slowing damage caused by digger zombies. I double up on jalepenos when bungee zombies are shown to be part of the next wave so to minimize their ability to steal plants. Not full proof but helpful. You just need an open lawn square which I allow in rows where I normally keep spike rocks.
I didn't think it possible on the iPad but you guys showed and taught me otherwise. I don't mean to be jaded but now I am in disbelief people hang on through hundreds of waves. I can imagine doing it on a pc because an extra plant slot can be earned that is not available in the iPad version.
Time to study longer term builds and shoot for one hundred waves. I got the alive and planting achievement but no trophy on the endless survival quick play game icon like all the other quick play challenges. Presuming this to be normal.