I want to join the royal signals, If later I wanted to later change to e.g. paras after a few years how easy would it be

Hi, capbadge transfer (ie changing from 1 capbadge (job) to another) is relatively common. There are a number of factors to this though and would very much depend on the time you'd be looking to transfer - ie have they got space for you, have they got space in the rank you may have reached etc. For the Paras you'd need a recommendation on fitness etc. It might be that instead of looking to transfer you look at remaining in the Signals but perhaps do P Company or the All Arms Commando course which would enable you to stay in your current capbadge but you'd be more likely to be pushed to do more work with 16 Air Assault Bde or could be attached to Cdo units thus getting the best of both worlds.