After effects is creating a lot of media cache files in application support/adobe/common. I dont recall this happening before. It gets very large. Firstly can I delete these and second can I move this folder onto an external drive as I have an SSD with very little spare memory.
You have options within AE to purge the cache.
You have options in your preferences to change the location AE uses for its cache. You want it on the fastest drive you have for optimum performance in AE, so I would recommend against an external drive for it. Instead, I would suggest limiting (in your preferences) how much room AE uses for its cache.
What you are talking about is the disk cache. I think this is different. This is a folder in application support called media cache files. Its separate to disk cache which I already have set up on external drive and already know how to purge in preferences.
There is the global persistent cache, yes, but there is also the conformed media cache. Both can be changed.