Drop in or Sign up ?!?

My initial research has revealed a vast number (most?) groups in Reigate are not drop-ins, and you have to sign up for a term which might become costly! When junior was little I found this hugely problematic as his napping was unpredictable, as were the various colds he happened to catch so we ended up paying for quite a few classes (Baby signing, swimming etc) which we couldn't attend. I also had issues with singing/story groups where the mums sang/listened while the babies/toddlers wandered around aimlessly or stared into space (and I did wonder how much junior was getting out of it!) Now that he does tend to nap regularly I am wondering how on earth I will know what he will like!! I'm hoping some groups will offer a free trial session but I will certainly be on the hunt for drop in groups - so please let me know if you can recommend any!