Laura writes about Ayutthaya
In Ayutthaya we stayed in a budget guest house (recommended by Lonely Planet) which was really nice and peaceful. The owner (a very friendly elderly lady, told us that the place is always booked out (she was getting another section build with more rooms to house more people). The place was full of backpackers! (must be due to the good reviews it gets in the Lonely Planet!).
We saw a few of the temples by bike and saw some other ones on a tuk tuk tour at night while we were there.
The train ride to Ayutthaya was interesting, especially the trains! Very slow as well!