Every few months my toilet appears to be blocked - water rises up the pan further than normal on flushing and then slowly drains away - the blockage is always outside in the inspection pit - never in the toilet itself. It takes just seconds to check this out and may save you time and effort if you look outside first.
If you have a pit and it's clear then you can either use pressure to try and force the obstruction through the waste pipe or poke a flexible rod or spring around the bend - DIY stores sell drain springs.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix toilets.